The following is adapted from an article written for a landscape and irrigation contractor’s magazine. Although oriented toward the professional irrigation installer, the principles shared here apply to anyone installing an irrigation system, and in many cases, other types of construction. Homeowner’s need to prepare a materials list too, so most of this applies to the do-it-yourself installer too. So whichever you are, week-end warrior, or future pro, read on!
Introduction to Irrigation Material Take-Offs:
Definition “Take-Off“: When used in construction a take-off is the term used to describe a list of materials needed for the project installation. It’s used primarily as a noun, sometimes a verb. Typical noun usage; “Hey Joe, where did you put the take-off for the Upa Creek Project?” or as a verb “Joan, I need you to take-off these plans before tomorrow.”
Tip: If you want to look like you have a clue when dealing with pros use the term “take-off” for your material list. If you want to look like an amateur (or you’re at a big box home-store) call it a parts list.
The material take-off for an irrigation system is likely to be the most time-consuming and disliked part of preparing a bid for most contractors. The job is tedious, strains the eyes, and is often downright boring. Often the job of preparing the take-off is passed on to the staff member with the least seniority and experience- probably the worst possible person for the job! Yet it is a demanding job that can make or break your bottom line. If expensive items are missed and left off the take-off you could lose thousands of dollars. The ideal person to prepare a take-off needs to have a broad knowledge of irrigation equipment and installation methods. Top tier companies that consistently rake in nice profits all use highly trained, experienced, and well-paid estimators for this job!
Each company should have a standard system for doing take-offs in order to promote uniformity, reduce errors, and speed the work along. This system should incorporate “double checks” wherever possible to help catch omissions and errors. The little extra time used to perform these double checks is cheap insurance when compared to the cost of furnishing 10 or 15 sprinkler heads not accounted for in the bid! For you do-it-yourselfers the savings comes from reducing those unplanned trips to the store for a couple of extra parts!
The last ingredient that every system for performing take-offs should have is a checklist of items normally found in irrigation systems. The alternative to a checklist is to use a take-off form that incorporates the checklist. That is the method that will be used here. The take-off form is located here: Irrigation Materials Take-Off Form, please download it and print a copy now. In order to give a better understanding of how such a take-off system would work, the following is a description of how this take-off system works. (Note: at the time this article was written the author operated a take-off preparation service that prepared take-offs for 15 irrigation supply houses. )
Want to be a professional irrigation installer? Read this! For the contractor it is important to realize that when you give a owner or general contractor a bid price on a commercial project, they expect that price to be accurate, and they expect that you will not change that price unless something changes that is beyond your control. “I left that out”, or “I didn’t see it in the plans or specifications” will not fly as an excuse. A general contractor, developer, and especially a homeowner’s association will not hesitate a moment before hauling you into court and bankrupting your company. It happens all the time. Commercial work is not for beginners!!! Learn the business and get a firm handle on costs someplace else that is more forgiving.
The take-off preparation starts by noting on the take-off form the project name, location, bid date, and the name and phone number of the irrigation system designer. This information can save valuable time later, should questions arise. Next the project specifications are carefully read, take notes on all important information relating to materials on the back of the take-off form. (Specifications are detailed written requirements used to define the scope of work on commercial and government construction plans. Just the irrigation portion is often 20-40 pages long! Often there are excruciatingly detailed instructions in these documents that must be followed to the letter, or you might not get paid for your work.)
Review the notes on the back of the form at the completion of the take-off process to assure compliance. As you read the “specs” especially look for items which conflict with the plans and will have to be resolved with the irrigation system designer. Often there are many conflicts. Another item to look for is “hidden items”– items called for in the specs but not shown on the plans, such as check valves and drain valves. These items can eat up profit margins fast if left out and typically they must be installed even if you missed them when bidding and they aren’t shown on the actual plans. Although properly prepared specifications should have material requirements listed in a separate section for easy reference, most specifications are not properly written. So its necessary to read the whole thing very carefully. You can really lose a lot of money fast if you miss something here. Government projects are particularly known for having lots of hidden items in the specs.
Take-Off Major Items:
Next tackle the plans or drawings. Using the take-off form, make sure that each item listed in the plan legend is on the form. Transfer any details from the plan onto the form, such as model numbers, and optional features specified on the plan legend or in the specs. If the item is not on the form, add it at the end. At this time do not worry about quantities, you just want to insure that every item listed on the legend or plan notes gets on the take-off form. After everything on the legend is noted on my form you’re ready to start counting quantities of items. Cover the plan with a sheet of transparent tracing tissue so that you can make marks and notes without defacing the actual plan. If you have an extra copy of the plan you can write directly on it. Don’t worry now about things that need to be measured (like pipe lengths) just concentrate on items that can be counted. Start at the top of the take-off form and work down, line by line. As each item is counted mark the symbol for it on the plan using a yellow, felt-tip underlining pen. That lets you know you already counted that item. When counting large quantities it helps to use a push-button counter, like those used by bus drivers, to keep track of the quantity. It’s really easy to get mixed up when counting, especially if someone interrupts you!
After all the items on the take-off form are counted make a brief check of the plans for any items not highlighted with the yellow pen. This allows you to catch items you missed. Often you will also find items that the designer left off of the legend. These are noted so they can be identified later by contacting the system designer. Also check the common items listed on the take-off form that you didn’t find on the plans. Did the designer forget something? Are any of these items going to be needed for installation of a workable system?
The next step is to measure the linear footage of just the main-line pipe. It’s easiest to use a precision measuring device with a little wheel on it. As I roll it across the plans it measures the distance covered. There are now some really fancy digital measuring tools for measuring distances that contain small calculators which automatically convert the scale distance on the plan to actual distance in the field! For the do-it-yourselfer a ruler will work just fine for measuring the pipe lengths. When measuring distances on blueprints it is important to remember that most blueprints are slightly larger or smaller than the original drawings, and site conditions often vary from the plans. In addition, each person has natural tendencies to measure either higher or lower than the actual quantity. If you don’t have any experience to guide you consider adding at least 2% to help offset any variances. Most irrigation material suppliers will allow you to return a reasonable amount of unused materials for credit, so it’s not going to cost much more for the convenience of extra materials on hand during the installation. When measuring the mainline it is important to double check for small off-shoots of the mainline that might not be obvious until you look closely at the plans. A couple of examples might be short mainlines leading to hose bibs near a trash enclosure, or quick coupler valves for hand watering baseball diamond infields.
Mainline fittings are the next item to receive attention. This is where a good understanding of installation methods and an ability to visualize the system on the ground are useful. As each fitting is counted, circle its location on the plan with a black pen. Again this helps keep track of what has been counted and what hasn’t. For most situations there are any number of fitting combinations that can be used. For example a tee fitting may be needed where a 1″ pipe comes in from one end, a 3/4″ goes out the opposite, and another 3/4″ goes out from the side. In this case there is a tee made with this exact configuration that you could use (1″ x 3/4″ x 3/4″). But you could also use a 1″ x 1″ x 3/4″ tee with a 1″ x 3/4″ reducer in the end outlet. Or you could use a 1″ x 1″ x 1″ tee with two, 1″ x 3/4″ reducers. This can get pretty confusing when you get out in the field and start trying to remember which combination you planned to use at each location. If you plan to install the system yourself, it’s a good idea to note down the fittings you choose to use in pencil on the plan so that later when you start installing you will use the same fitting combinations. How do you know which fitting size combinations are available? There is a form that lists all the common ones for you! Irrigation Fittings Take-Off Form.
Next count the lateral line fittings, if needed. Don’t forget to circle each fitting location on the tracing paper as you add the fittings to your fittings take-off form so you don’t forget what you’ve counted! For contractors bidding on work you will generally NOT make a lateral fitting count. Chances are the system will not be installed exactly as designed due to minor variations in the field. A reasonably accurate estimate of the fitting costs can be made by using a percentage of the lateral pipe costs, usually something in the range of 30-45 percent. Experience will allow you to fine tune this percentage and many estimators become very accurate with time. Another good approach is to ask your local irrigation supplier what percentage of pipe cost works well in your area. They often have a really good handle on this info and can be very helpful. Remember your professional irrigation supply store is your partner in business, find one you like, work with one as exclusively as possible, and tap into their knowledge and help resources.
In order to accurately measure the quantities of each size lateral pipe, try using a color coding method. For small residential systems this is unlikely to be necessary, but on larger systems it can help preserve your sanity. Using inexpensive children’s felt tip coloring pens, trace the entire piping system onto the tracing paper. For each pipe size use a different color of pen. Although this is time-consuming, the increased accuracy justifies the effort. (An added benefit is that when people see your plan with all those pretty colors they complement you on your coloring ability. ) In the process of tracing the pipes you will often come across sprinklers that you missed counting earlier (they don’t have the yellow mark on them). Sometimes you will notice a design error, such as a missing sprinkler head, which you should make a note of . This way you can point it out to the designer which relieves you of liability for any dry spots and often leads to additional work and payments (cha-ching $$$, extras are profitable because you are now in a position of control!) Thus tracing the pipe is one of the double checks used for accuracy. Now you have a color coded drawing which makes measuring the quantity of each pipe size much easier. If you used red pen for 3/4″ pipe you can easily spot all the red pipe and measure it at the same time. That is much faster and easier on your eyes than trying to pick out individual 3/4″ pipes on a plan with hundreds of pipes of many sizes. On really large plans use a black pen to divide the plan into smaller sections, and measure the pipe one section at a time. This helps keep track of what you have already measured so you don’t get lost.
This is a good point to do a quick check of the plan for anything you missed counting and then remove the tracing paper. Then measure the control wire needed for the automatic valves. On a standard style solenoid valve system (not a “2-wire system”) the first control wire to measure is the common wire. This wire goes from the controller to the first valve, then the wire continues on to the next valve, the one after that, etc., until it has reached the last valve. In other words, all the valves are connected to the same wire, which is why it is called the “common” wire. Industry standard practice is to use a wire with a white insulation on it for easy identification as the “common” (this is a universal standard.) If you have multiple controllers, each controller requires it’s own separate common wire. When using multiple common wires use white wires that each have a different color stripe on them to identify the different wires. Never connect the same common wire to more than one controller, the power feedback can burn out the circuitry in some controllers! If a spare wire is required it will be the same length as the common wire, so you can save a little measuring. Consider always installing at least one spare wire just in case something happens to one of the wires during installation. That way you don’t have to waste lots of time trying to find the break in the original wire, just use the spare wire.
The next wires to measure are the lead wires (pronounced “leed”.) One lead wire goes from each valve to the controller. In other words, there is one lead wire for each valve. Lead wires can be any color other than white. Red and black are the most commonly used colors. As with measuring the pipe use a small measuring wheel to measure the wire lengths. Be sure to include extra wire for making the connections at the valve and controller! Also make sure there are no stub-outs for future valves shown on the plan. If there are, you will need to include wires for each of the future valves also! For smaller systems a different color wire can be used for each valve. Often residential systems use a multi-wire cable. This cable contains several wires in a single jacket. If you use cable you need a cable with one wire for each valve plus the common. So if you have 5 valves you will need a 6 wire cable. I suggest that you also leave at least one wire in the cable unused for a spare, so you would then want a 7 wire cable.
Next I measure any sleeves needed for wires or pipes under paving. The sleeve size for pipes needs to be twice the diameter of the pipe inside it. Remember that the couplings between pipe sections need to fit into the sleeve also, and they are much larger in diameter than the pipe! For wire sleeves the size varies with the size of the wire and the number of wires in the sleeve. Don’t try to cram a lot of wires into a small sleeve. Leave lots of extra room to make it easier to feed the wires into the sleeve.
Now make a quick review of all the notes on the plans to make sure nothing is missed and then move on to the detail drawings. The detail drawings show how various small assemblies are to be constructed. For example a valve detail is often provided on the plans showing exactly how the valves are to be installed. There are a number of sample details for do-it-yourselfers included later in this tutorial. You should find an appropriate detail there to guide your installation. Using these details as a guide calculate the various fittings, valve boxes, wire connectors, etc., that will be required to install the valves, backflow preventers, sprinklers, etc. Almost every piece of equipment needs related materials to be installed. For example, a typical valve needs short lengths of pipe leading to the valve, inlet and outlet fittings, a valve box, some gravel to line the bottom of the box, and wire connectors for making waterproof wire splices. Again, as a double check start at the top of the take-off form and work down it one item at a time, checking to make sure you have included all the related items needed to install each piece of equipment.
The last items to go onto the take-off are the many small but necessary miscellaneous materials that can really add up to big costs if left off. These include items like PVC cement, wire splice waterproofing kits, thread sealant, etc. Most of these are listed on that standard take-off form you downloaded earlier. A final review of the take-off form is then made and the take-off is complete! Of course, there is a checklist for you to use listing frequently missed items. Irrigation System Materials Checklist.
When contractors are bidding on large projects it is recommend that they use two take-offs, each made independently by a different person, and compare the take-offs to find errors. While it is possible to simply reviewing someone else’s take-off it doesn’t work as well, the power of suggestion seems to result in the reviewer obtaining the same errors as the original take-off preparer. Often contractors can get their irrigation material suppliers to provide at least a minimal take-off to use as a double check for large jobs. Irrigation supply stores want to sell the materials for those large projects so they are often willing to help out. There are also outside consultants who prepare take-offs for a fee. They often advertise their services in the classified sections of trade publications.
Finally, when preparing a take-off remember to be careful. Don’t hurry. Use a checklist or take-off form to guide you. Double check your figures, and last but not least take a tip from professional accountants and always use a calculator for all of your math (a printing calculator where you can save the tapes is even better)!
This article is part of the Sprinkler Irrigation Installation Tutorial Series
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