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Irrigation Mainlines

Irrigation Mainline.

Definition of irrigation mainline: The mainline is all the pipes between the water source and the irrigation zone control valves. Another definition is that mainline is any pipe that is always pressurized with water.

Your water source may be a water company pipe in the street or alley, or it could be a pump, a well, lake, pond, stream, tank, or whatever. If the same water source is used for both residential water and irrigation, you will likely have two mainlines. There will be an existing house mainline which goes from your water source to the house. The irrigation mainline connects into this house mainline to draw off the water for the irrigation system. The irrigation mainline takes the water from the house mainline to the irrigation valves.

The irrigation mainline pipe is the major pipe in your sprinkler system, so it is typically to use a higher quality of pipe when installing it. The mainline often has higher water pressures in it and also has a lot more pressure surges in it. Typically it always has pressurized water in it, so if it breaks a lot of water may be wasted before the break gets noticed and repaired. Most pipe has a pressure rating aligned to it. This rating is the maximum pressure the pipe can withstand without risk of breaking. Because of the higher demands on the mainline, normally the pressure rating of the pipe you use for mainline should be double the actual water pressure. This may sound like over-kill at first, however huge pressure surges in an irrigation system are a normal occurrence so you need to design the system to withstand them. Pressure spikes of twice the normal pressure may occur every time a sprinkler control valve is closed. That's a lot of pressure spikes, and each one puts a huge stress on the pipe. Using a higher pressure rated pipe allows for a margin of safety and helps reduce the frequency of pipe breaks. Breaks are difficult and expensive to repair.

Local building codes may dictate what type and pressure rating of mainline pipe you must use. In most areas I have worked in the building officials do care what you use for irrigation system mainline, if the mainline is after both an emergency shut-off valve and a approved backflow preventer. On the upstream side of the backflow preventer (the side the water is coming in from) the Uniform Plumbing Code requires that the pipe be the same type as used for local homes. Before you decide to do your own thing with the mainline after the backflow preventer it is best to check the local requirements. While most don't care, in some areas the building officials are very picky about what type of pipe you use for the entire mainline. This is especially true for areas where water is in short supply, as in these areas officials want to avoid possible leaks from poor quality mainlines. Please call them up and ask as it is very expensive when they discover you used an unapproved pipe and they make you remove it.

Types of mainline pipe:

PVC Plastic. SCH 40 PVC pipe is the default pipe used for mainlines throughout the western and southern areas of the USA and is also used in most other temperate climates. When using PVC plastic pipe for your mainline, in most cases I would recommend you use "Schedule 40" (SCH 40) PVC pipe with the letters UPC and NSHF stamped on the pipe for new mainlines. In most areas the requirement for the type of pipe are written into local laws. Often the local authorities will require that 2" size and larger mainline be CL 315 PVC, check with local building officials. For pipe sizes larger than 2 inch, Cl 315 PVC pipe is stronger than SCH 40 PVC.

Polyethylene (poly) Tube. In areas where the soil freezes to a depth greater than 6" heavy wall (rated 125 PSI) polyethylene tube has been used for many years. "Poly tube", as it is often called, is a flexible black plastic tubing which bends easily and has a slightly oily feel to it. You can easily scratch the soft surface with your fingernail. Polyethylene holds up better to freezing than PVC does. However, polyethylene as a general rule has a low pressure rating, and thus is subject to bursting and splitting open. Using polyethylene for mainlines is somewhat outdated now. New, tougher materials such as PEX tube (see next paragraph) are replacing it. I do not recommend that you use poly pipe for mainlines. "Irrigation poly tube" is a lower quality, low pressure rated tube made for low pressure irrigation laterals. Do not use it for mainlines.

PEX tubing. PEX tube is now used in place of polyethylene mainlines in much of the world and use of it is expanding rapidly. PEX is a form of polyethylene which is reinforced to make it stronger while maintaining good flexibility. Be aware that PEX tube has less carrying capacity than polyethylene (as well as most other tubes and pipes), so you will need to use a larger size of PEX tube than you would have used for polyethylene. PEX is often sold as an equivalent to copper tube, because it has the same outside diameter and can use compression type fittings similar to those used for copper tube. However in regards to flow capacity PEX has a much thicker tube wall and thus the area inside for the water to flow through is smaller. This smaller inside area results in considerably less water capacity than copper. So if you replace a 1" copper tube with a 1" PEX tube you may discover a large drop in water capacity and pressure through the tube. As a general rule, when replacing a existing copper tube with new PEX tubing I feel it is best to increase the PEX tube size to be one size larger than the copper tube was. It is easy to see why this is an issue if you compare a piece of copper tube and PEX tube side-by-side. While the outside dimensions are identical, you will see that the PEX is much smaller inside.

Metal pipe or tube. You can also use copper or galvanized steel pipe for new mainlines if you wish. Copper is expensive, but a great choice as it is very durable. Galvanized steel is not such a great choice, it corrodes from the inside and will slowly choke off the flow over time. Galvanized steel also flakes off bits of rust which can cause problems with irrigation systems. Early irrigation systems used galvanized steel pipe, but the use was mostly stopped in the 1960's.

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Pressure Loss Calculations

Common question: "Can I skip calculating the pressure loss in the house mainline? It is upstream of where I measured my pressure."   NO, NO, NO! Sorry to yell at you, but it's a huge, common mistake, so I want your attention. When you measured the water pressure you measured static pressure, that is, the pressure when the water is not moving. There is no pressure loss when the water is not moving. But when you run the sprinklers the water will be moving, so there WILL be pressure loss in the house mainline as well as the irrigation mainline. Often the pressure loss in the house mainline is substantial. Therefore you must also calculate the pressure loss for the house mainline and add it in with your other pressure losses. Think of it this way- we call the loss "friction loss" and there isn't any friction when the water is not moving! Why not measure the pressure with the water flowing (dynamic pressure)? Because it is pretty difficult to get the correct flow rate and you would likely need to disassemble part of your house piping and build a special test pipe to get an accurate measurement. Not convinced? You're going to need to trust me on this one, or take a college level course in hydraulics.

Any new mainline pipe should be installed at least 18" deep, or below the frost level*, in order to meet code requirements.

*If you drain or blow the water out of your mainline each winter you do not need the mainline to be below the frost line. However it still should be at least 18 inches deep to protect it against damage (ie; digging holes for plants) and from unexpected early or late season freezes. Remember the mainline contains high-pressure water so if it is broken it will create a geyser and a big mess in a hurry. The force of the water can break nearby windows if it tosses small rocks out of the ground along with the water. If you plan to drain or blow out the mainline you will need a shut-off valve located someplace where the valve will not freeze (or you can use a special freeze-proof valve, or use a heating cable to prevent it from freezing.) Most people put the shut-off valve in the basement or a heated shed/pump house. I strongly recommend that you use a brass body ball-valve for the shut-off valve (or a special frost-proof designed valve.) Gate valves are not a good choice, they tend to leak after a few uses.

In some cases you may have two (or more) different pipe sizes or types between the water source and irrigation valves. For example, you may have a 1" copper house mainline and a 1 1/4" PVC irrigation mainline. Often it is advantageous for the irrigation mainline to be larger than the house mainline. In any case, you will need to calculate the pressure loss separately for each different pipe size and type, then add them all together.

Example: You have a 1" polyethylene "house mainline" that starts at the water company's main (a large water company pipe in the street that supplies water to all the houses in the neighborhood). Your polyethylene house mainline tube takes the water to the water meter and then continues to take it on to the house. At the house the mainline becomes copper, and extends into the basement then on to all the various faucets in the house. You decide to tap into this copper tube in the basement for the irrigation system water. You install a new 1" copper irrigation mainline which goes to a backflow preventer in the basement and the copper continues through the basement wall back outside again. Finally you use an adapter to attache a new 1 1/4" PEX "irrigation mainline" to the copper mainline just outside the house. The PEX mainline runs a short distance across the yard to the location of the irrigation control valves. OK, here's what you do. You will need to calculate the friction loss for each of those sections of pipe or tube separately, then add them all together for the total mainline pressure loss.

1" poly house mainline to meter and then continuing to house
+ 1" copper house mainline
+ 1" copper irrigation mainline to backflow preventer and out through wall
+ 1 1/4" PEX irrigation mainline to the valves
= Total mainline pressure loss

Here's a common problem. You need to know the length of all these pipe sections. Some are easy, you can see them and measure the length. Others are not so easy, you can't see them and they may be under a street or driveway. So, if the water company pipe that your house mainline comes from is somewhere out it the street, how do you know where it is so you can measure the length of your house mainline? You will probably need to make an educated guess. Look up and down the street for manhole covers labeled "water". Generally they are located directly over the pipe, and the pipes in most cases run parallel to the street curbs. If you can find two manholes, the pipe generally runs in a straight line between them. I know that's not real helpful, and there is one other trick that sometimes works. If you call the water company they may be willing to send someone out to mark the water company main location for you on the street using paint.

So how are you supposed to know the length of your irrigation mainline before you even design the sprinkler system? At this point you probably don't know how many valves you will need or where they will be located, so how can you know how long the mainline going to them will be? Good question! The answer is that you are going to need to guesstimate. As discussed above, the irrigation mainline essentially goes from the point of connection (that's the place where you tap into the existing water pipe for the new irrigation water supply) to the sprinkler control valves. So ask yourself where would you like for the control valves to be? Globe valves can be installed underground in a box almost anywhere you want, although in most cases it is best if they are near (but not within) the area that they will be watering. Anti-siphon valves need to be at the highest area of the yard, so you know you will need to run the mainline to them at the high spot. Another thing is to try to use as little mainline as possible. The mainline pipe is expensive and harder to install, so you want to keep it minimal. Also keep in mind that with an automatic irrigation system the valves don't need to be in a single group. While I suggest you install them in small groups for convenience, it is perfectly fine to have several groups in various areas of the yard. Perhaps an example will help!

So let's say you have a typical house where the water supply pipe comes from the street and runs to the house. You decide to tap into the water supply for the irrigation system in the basement, right after the pipe comes in from the yard. So your "point of connection" is in the basement. From there the irrigation mainline would run out through the basement wall to, say, the front yard. The part of the irrigation mainline that is within the basement should be metal or PEX pipe (not all local building officials allow PEX pipe in a basement, so check first.) Many people install their backflow preventer in the basement also. That is what we will be doing for our example. So we will put a reduced pressure backflow preventer on the new mainline before it leaves the basement. (Since it is a reduced pressure backflow preventer we also assure that there is a drain inlet in the basement floor, as they sometimes spit out water onto the floor.) From the backflow preventer the metal irrigation mainline pipe continues through the wall and out to the yard. Be sure to seal and water-proof the hole through the wall around the pipe! After the irrigation mainline is through the wall the metal pipe should extend another 12 inches beyond the edge of the wall, then you can change to plastic pipe using an adapter. If the adapter uses threads make sure the female threads are metal, and the male threads are plastic. If you use plastic female threads with metal male threads the hard metal male threads will expand ad contract with temperature changes and cause the soft plastic female end to split open. If the pipe comes out of the wall above ground it will need to be metal until it is a few inches underground. Plastic pipe should never be used above ground where it would be exposed to sunlight. Sunlight will degrade it and cause premature failure.

You plan to water the front yard with the new sprinkler system, so you will need some control valves for the front yard. If you are using anti-siphon valves you don't have a lot of choice as to where they are installed. They must be installed at the highest point in the front yard. In this case we are using a reduced-pressure type backflow preventer in the basement and standard globe-type control valves out in the yard, so we don't need the valves at the highest point. Where the new mainline comes through the wall there is already a big group of shrubs, perfect to hide the valves in. So the mainline will come out of the basement and extend to the front yard valves, which we will install underground in a box hidden by the shrubs. So far, so good. Hopefully you are now starting to get a mental image of what your irrigation system might look like.

Now let's say you also want to water the backyard. You could put the valves for the backyard near the same clump of shrubs with the front yard valves. But this would mean lots of pipes going to the backyard from the front. Plus it would be inconvenient- if you needed to work on the backyard sprinklers, you would have to walk all the way around to the front yard each time you wanted to turn on the valve. So the best solution is usually to continue the mainline from the front yard, around the house, to the back yard. Some people choose to run the mainline under the house in the crawl space, through an unfinished basement, even through an attic- this is OK but you should use metal or PEX pipe under or in the house. The type of pipe under or in the house must meet building code requirements.) You can even use metal pipe and strap it on the outside wall of the house, but it looks a little ugly! Now the question is where to put the valves for the backyard? As with the front yard, if you plan to use anti-siphon valves you must install them at the highest point in the back yard. So your choice is already made for you. If you plan to use a backflow preventer and globe valves, then the choice of valve locations is up to you. Again, a good location is someplace out of the way, but also near the area they will control the water in. A good place for the valves is along the perimeter of the yard. I like to run my mainline about 24 inches away from the property line. Usually a shrub border is planted at the perimeter of a property, so this also works well as a way to hide the valves.

One last note- it is best not to locate a valve within the area that is watered by the sprinklers that the valve turns on and off. If you do, you are probably going to get sprayed by the sprinklers when you turn them on. This is not fun.

Calculating the Mainline Size

What size should your new irrigation mainline be? I wish there was an easy answer, but, unfortunately, you will need to start with an educated guess. Then you need to calculate the total pressure loss in your mainlines and add it to all of your other pressure losses in the sprinkler system. If the pressure losses are too great, you may then need to increase the size of your new mainline. Using a larger size pipe means there will be less pressure loss as the water squeezes through it. More on that later. Unfortunately, there are no "magic" ways to determine what size a pipe should be. Pipe size is based on many different variables, what works at one house may not work next door! Don't panic, it is easier than it sounds and I will lead you through it step-by-step!

As previously stated, you need to start with an educated guess for the irrigation mainline size. Almost always the irrigation mainline will need to be the same size or larger as the house mainline, so that is one good place to start. Even better, start with one size larger than the house mainline as in most cases this will be needed, especially if your Design Pressure is less than 50 PSI. Another good starting point is one size larger than the water meter if you have a meter (use 2 sizes larger if the pipe is polyethylene or PEX.)

Remember that with sprinkler system pipes a bigger pipe almost never hurts anything and is almost always better. Using a larger size pipe will not hurt anything except in a few very, very rare situations. The chance of you actually having one of those situations is close to zero. On the other hand, using a smaller pipe can hurt in many situations. This seems illogical, and you will run into a lot of professional sprinkler folks who will swear that a smaller pipe is needed to increase water pressure. They did not learn this in school! It is not true. They aren't bad people, they were probably taught this by whomever taught them irrigation, and the irrigation-myth gets passed along again and again, taking on a life of it's own. Here's the science-based truth: When you make the pipe smaller and try to force the same amount of water through it, the water must travel faster (higher velocity) to squeeze through that smaller pipe. Bernoulli's Principle states that as the speed of a moving fluid increases, the pressure within the fluid decreases. Decreasing the size of the pipe will not create more water pressure, it does just the opposite. You can test it yourself- go to Mark Mitchell's Animated Demonstration of Bernoulli's Principle where there is a fantastic, free, interactive graphical demo that allows you to change the size of a pipe and see what happens to the velocity and pressure. It's fun, and a picture is worth a thousand words!

Hose Bibs and Yard Faucets

One more item to quickly remind you of. I strongly recommend that you do not use a hose bib or faucet on your house as your irrigation water source. It is best if you avoid running the irrigation water through the house. Connect to the house mainline between the water source and the house if possible. If you do need to install a backflow preventer in the basement, tap into the water supply as close as possible to the point where it enters the basement. You can then run a new pipe for the irrigation under or around the house if you want to get the water to the back yard. Most existing pipes inside the walls of houses are too small to handle the volume of water needed for an irrigation system. Those pipes are intended to supply the much lower flow requirements of household appliances, faucets, and showers. If you force more water through those pipes, the high flow velocity can create pin-holes in the house pipes. These pin-holes are extremely expensive to repair! Often the only fix is to completely replace the pies or install a plastic coating on all the pipe in the house. Plus the noise of the water flowing through the pipes when the sprinkler system is running may drive you nuts! It can be very loud.

Looped Mainlines

If you have a large yard it may be beneficial to use a looped irrigation mainline. Typically there is no benefit to this on a smaller residence, but if you have a big country estate with lots of irrigation it may be worth looking into. If you have more than an acre of property I would suggest you take a look at the tutorial How to Design a Looped Mainline for Irrigation Systems.

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How to calculate pressure loss

Water pressure loss in pipes is calculated by using the pipe size and the flow rate of the water through the pipe. This website has several calculators you can use, or you can do it the old-fashioned way and use the tables at the bottom of this page.

Spreadsheets for Calculating Friction Loss

I've created a whole collection of spreadsheets for doing the friction loss calculations for various types of pipe and tubing. Hopefully you will find these spreadsheets pretty easy to use, I tried to make them do as much of the work for you as possible. They will calculate both pressure loss and velocity, and will warn you if the flow you have selected is too high. Spreadsheets are available for pretty much all the common types of pipe found in homes today. Spreadsheets for Calculating Friction Loss & Pressure Loss in Pipes and Tubes.

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Stand-alone Windows Pressure Loss Calculator

There is also a free stand-alone Windows friction loss calculator available, which was created by Steve Granger. Use the value of 1 for both the Specific Gravity and the Viscosity of water when using this calculator. Under the heading Material, "Plastic" is PVC plastic. The current version doesn't work for poly plastic. The windows calculator will calculate friction losses for galvanized steel several other materials in addition to plastic. Download the calculator from http://www.IrrigationTutorials.com/LineSize.exe. Many thanks to Steve for creating this calculator and providing it free for everyone to use.

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Pressure Loss Tables

Here are some old-fashioned pressure loss tables you can use to calculate the friction loss in your mainline. This is the old-school, low tech method.

How To Use a Pipe Pressure Loss Table:

(PSI = pounds per square inch = lbs./sq.in.)

• Select the proper table for the type of pipe, i.e.; SCH 40 PVC, SCH 40 Steel, Polyethylene, copper, etc.
• Locate the proper column on the table for the pipe size.
• Read down the column to the row for the flow rate (GPM) in the pipe section. You will find a PSI loss value (given as PSI/100).
• Multiply the PSI loss value shown by the total length of the pipe section, then divide the product by 100. (PSI loss on these tables is given in PSI per 100 feet of pipe.)
• Pressure loss values in yellow are over 5 feet per second. This is a high velocity, but considered acceptable for short distances (less than 50 feet of pipe length.)
• Pressure losses greater than those shown on the chart can cause permanent and expensive damage to your plumbing. You must use a lower flow (GPM) in the pipe.

PSI Loss Value x Length of Pipe / 100 = PSI loss in pipe

Example: 1" size, type SCH 40 PVC mainline. The length of the mainline pipe is 23 feet. The water flow rate through the mainline is 18 GPM. Using a pipe pressure loss table we find that the PSI loss for 1" SCH 40 PVC at a flow rate of 18 GPM is 8.12 PSI per 100'. Therefore:   8.12 x 23 / 100 = 1.87 PSI - to simplify, you can round up the value to 2 PSI loss

(Note: PSI loss charts vary somewhat from each other. Other charts may result in an answer slightly different from the one in this example.)

PRESSURE LOSS TABLE FOR SCH 40 PVC PIPE

FLOW GPM	3/4"	1"	1 1/4"	1 1/2"	2"	2 1/2"	3"
1	0.13	0.04	0.01	------	------	------	------
2	0.45	0.14	0.04	------	------	------	------
3	0.95	0.30	0.08	------	------	------	------
4	1.62	0.50	0.14	0.07	------	------	------
5	2.45	0.76	0.20	0.10	------	------	------
6	3.44	1.06	0.28	0.13	------	------	------
7	4.57	1.42	0.38	0.18	------	------	------
8	5.85	1.81	0.48	0.23	------	------	------
9	7.28	2.25	0.60	0.28	0.09	------	------
10	8.85	2.74	0.72	0.34	0.11	------	------
11	10.56	3.26	0.86	0.41	0.12	------	------
12	------	3.84	1.01	0.48	0.14	------	------
13	------	4.45	1.17	0.56	0.17	------	------
14	------	5.10	1.35	0.64	0.19	------	------
FLOW GPM	3/4"	1"	1 1/4"	1 1/2"	2"	2 1/2"	3"
15	------	5.80	1.53	0.72	0.22	0.09	------
16	------	6.53	1.72	0.82	0.25	0.11	------
18	------	8.12	2.14	1.01	0.30	0.13	------
20	------	------	2.60	1.23	0.37	0.16	------
22	------	------	3.10	1.47	0.44	0.19	------
24	------	------	3.65	1.72	0.51	0.21	0.08
26	------	------	4.23	2.00	0.60	0.25	0.09
28	------	------	4.85	2.29	0.68	0.29	0.10
30	------	------	5.51	2.60	0.78	0.33	0.12
35	------	------	------	3.46	1.03	0.44	0.15
40	------	------	------	4.43	1.32	0.54	0.20
45	------	------	------	------	1.64	0.69	0.24
50	------	------	------	------	1.99	0.84	0.30
55	------	------	------	------	2.37	1.00	0.35
60	------	------	------	------	2.79	1.18	0.41
FLOW GPM	3/4"	1"	1 1/4"	1 1/2"	2"	2 1/2"	3"
65	------	------	------	------	3.23	1.36	0.48
70	------	------	------	------	3.71	1.56	0.55
75	------	------	------	------	------	1.78	0.62
80	------	------	------	------	------	2.00	0.70
85	------	------	------	------	------	2.24	0.78
90	------	------	------	------	------	2.49	0.87
95	------	------	------	------	------	2.75	0.96
100	------	------	------	------	------	3.02	1.05
110	------	------	------	------	------	------	1.26
120	------	------	------	------	------	------	1.47
130	------	------	------	------	------	------	1.71
140	------	------	------	------	------	------	1.96
150	------	------	------	------	------	------	2.23
160	------	------	------	------	------	------	2.51
FLOW GPM	3/4"	1"	1 1/4"	1 1/2"	2"	2 1/2"	3"

Pressure losses shown in yellow reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.

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PRESSURE LOSS TABLE, POLYETHYLENE PIPE

Flow in GPM	3/4"	1"	1 1/4"	1 1/2"	2"
1  GPM	0.12	0.04	0.01	0.00	0.00
2  GPM	0.45	0.14	0.04	0.02	0.01
3  GPM	0.95	0.29	0.08	0.04	0.01
4  GPM	1.62	0.50	0.13	0.06	0.02
5  GPM	2.44	0.76	0.20	0.09	0.03
6  GPM	3.43	1.06	0.28	0.13	0.04
7  GPM	4.56	1.41	0.37	0.18	0.05
8  GPM	5.84	1.80	0.47	0.22	0.07
9  GPM	7.26	2.24	0.59	0.28	0.08
10  GPM	8.82	2.73	0.72	0.34	0.10
	3/4"	1"	1 1/4"	1 1/2"	2"
11  GPM	10.53	3.25	0.86	0.40	0.12
12  GPM	12.37	3.82	1.01	0.48	0.14
13  GPM	13.34	4.43	1.17	0.55	0.16
14  GPM	16.45	5.08	1.34	0.63	0.19
15  GPM	18.70	5.78	1.52	0.72	0.21
16  GPM	21.07	6.51	1.71	0.81	0.24
17  GPM	23.57	7.28	1.92	0.91	0.27
18  GPM	26.21	8.10	2.13	1.01	0.30
19  GPM	28.97	8.95	2.36	1.11	0.33
20  GPM	31.85	9.84	2.59	1.22	0.36
	3/4"	1"	1 1/4"	1 1/2"	2"
22  GPM	38.00	11.74	3.09	1.46	0.43
24  GPM	44.65	13.79	3.63	1.72	0.51
26  GPM	51.78	16.00	4.21	1.99	0.59
28  GPM	59.40	18.35	4.83	2.28	0.68
30  GPM	67.50	20.85	5.49	2.59	0.77
32  GPM	76.06	23.5	6.19	2.92	0.87
34  GPM		26.29	6.92	3.27	0.97
36  GPM		29.22	7.69	3.63	1.08
38  GPM		32.30	8.50	4.02	1.19
40  GPM		35.52	9.35	4.42	1.31
	3/4"	1"	1 1/4"	1 1/2"	2"
42  GPM		38.88	10.24	4.83	1.43
44  GPM		42.43	11.16	5.27	1.56
46  GPM		46.01	12.12	5.72	1.70
48  GPM		49.79	13.11	6.19	1.84
50  GPM		53.70	14.14	6.68	1.98
55  GPM			16.87	7.97	2.36
60  GPM			19.82	9.36	2.77
65  GPM			22.98	10.86	3.22
70  GPM			26.36	12.45	3.69
75 GPM			29.96	14.15	4.19

Pressure losses shown in yellow reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.

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COPPER PIPE AND TUBE

Type K copper pipe has the thickest wall and highest pressure ratings of the common copper tubing types. In order of wall thickness, common copper tubing types are Type M (thinnest), Type L, and Type K (thickest). Type L is commonly used for household plumbing. If you don't know what Type the pipe is, assume it is Type K.

Flow in GPM	1/2"	3/4"	1"	1 1/4"
1  GPM	1.20	0.23	0.05	0.02
2  GPM	4.33	0.77	0.18	0.06
3  GPM	9.17	1.65	0.38	0.13
4  GPM	15.67	2.78	0.68	0.22
5  GPM		4.21	1.02	0.33
6  GPM		5.90	1.44	0.46
7  GPM		7.84	1.90	0.61
8  GPM		10.03	2.46	0.78
9  GPM		12.48	3.03	0.97
10  GPM		15.15	3.68	1.18
11  GPM			4.40	1.41
12  GPM			5.17	1.66
13  GPM			6.00	1.93
14  GPM			6.88	2.21
15  GPM			7.81	2.51
16  GPM			8.42	2.83
17  GPM			9.42	3.16
18  GPM				3.52
19  GPM				3.89
20  GPM				4.28
22  GPM				5.10
24  GPM				5.99
26 GPM				6.95

Pressure losses shown in yellow reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.

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PRESSURE LOSS TABLE, TYPE L COPPER PIPE OR TUBING

Flow in GPM	1/2"	3/4"	1"	1 1/4"
1  GPM	0.95	0.16	0.04	0.02
2  GPM	3.44	0.57	0.15	0.06
3  GPM	7.29	1.20	0.33	0.12
4  GPM	12.41	2.05	0.56	0.20
5  GPM	18.77	3.09	0.85	0.30
6  GPM		4.34	1.18	0.43
7  GPM		5.77	1.58	0.57
8  GPM		7.39	2.02	0.72
9  GPM		9.19	2.51	0.90
10  GPM		11.17	3.05	1.10
11  GPM			3.64	1.31
12  GPM			4.28	1.54
13  GPM			4.96	1.78
14  GPM			5.69	2.04
15  GPM			6.46	2.32
16  GPM			7.28	2.62
17  GPM			8.15	2.93
18  GPM			9.06	3.25
19  GPM				3.60
20  GPM				3.96
22  GPM				4.72
24  GPM				5.55
26 GPM				6.43

Pressure losses shown in yellow reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.

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By using this tutorial you agree to be bound by the conditions and limitations listed on the disclaimer page.

 

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