To put things in perspective, let’s think about what needs to happen in this area to make the system work. We’ll need a pipe to get the water from the wellhead to the tank, and on into the house. We’ll need to provide some sort of control to turn the pump on and off, and a check valve between the tank and the wellhead to prevent the tank from draining back into the well when the pump shuts off. We’ll need to have a pressure gage to know how the system is performing, and a pressure-relief valve (PRV) to protect the system, in case the pump controls fail and the system starts to build too much pressure. Finally, we’ll need a drain valve to drain the tank for servicing.
Setting the TankThe pressure tank needs to sit on a solid surface. If it is in a basement or garage with a concrete floor, no additional support is needed. If it is outside, some sort of solid pad will be needed. Most pump wholesalers carry either plastic or lightweight pre-cast concrete appliance pads that can be easily carried to the job site, and are much easier to install than pouring a pad. They particularly are useful if you are in an area where freezing is not a problem, and the tanks are installed outside where you do not need a big pad for a pump house.
The pressure tank also needs to be accessible for servicing. Today’s pre-charged captive-air tanks are built to last 10 years and longer, but they eventually will need to be replaced, so make sure you leave room to get the tank out.
Plumbing the Pressure TankThe decision as to what type of piping to use – PVC, galvanized steel or copper – depends on local codes and personal preference. I like galvanized steel or copper because it is stronger, and less likely to be broken if someone kicks it or drops something on it. Many pump installers use PVC in the pump house, and it works fine as long as it is protected from outside forces. It is much faster and cheaper to install. Check your local codes to make sure that the type of plumbing you plan to use is approved.
The Tank ConnectionSome installers fabricate the tank connections out of galvanized fittings. My preference is to use one of the specialized stainless steel, lead-free brass or galvanized tank tees offered by the water well accessories manufacturers because they eliminate five or six joints, which could leak, and they save time. For future serviceability, be sure to install a union between the tee and the tank, or on both sides of the tee so that, when it comes time to replace the tank, you don’t have to cut out your old plumbing. It is important that all of the materials used to connect the tank be electrolitically compatible. In other words, if you are using galvanized plumbing, use a galvanized tank tee. If you are using copper piping, use a brass tank tee.
Whether you use a prefabricated or cast tank tee, or make your own, you need to provide four outlets for the following:
- 1⁄4-inch tap for a pressure gage,
- 1⁄4-inch tap for a pressure switch,
- 1⁄2- or 3⁄4-inch tap for a pressure relief valve, and
- 1⁄2- or 3⁄4-inch tap for a drain valve.
Pressure-relief Valves (PRVs)The purpose of having a PRV is to protect the system, and the people and property in the vicinity of the system from damage, should something go wrong and the pump build up too much pressure. The most common failure that can cause the system to over-pressurize is for the pressure switch to stick in the on-position. Remember that some submersible pumps, particularly those designed for deep wells, are capable of producing hundreds of pounds of pressure. I have seen pictures of a pump house roof blown off when a pressure tank exploded because the pressure switch stuck, and there was no PRV on the system. Always install a pressure-relief valve, and always make sure it is large enough to handle the output of your pump. A 1⁄2-inch PRV is not large enough to protect a 55-gpm pump.
Check ValvesIt is necessary to install a check valve between the tank and the well to prevent the contents of the tank from draining back into the well when the pump shuts off. Depending on the depth of the well, you will have at least one additional check valve in the well as we discussed in earlier articles, but it still is good practice to install one aboveground where it is more accessible, and provides additional assurance that the water in the tank will not drain back into the well. A check valve at the tank also helps to minimize the possibility of water hammer as the pump cycles on and off. All pumped water system check valves should be the spring-loaded type, and not swing-check valves.
System Isolation ValveIn order to be able to service the system without having the water in the house drain back when the plumbing at the tank is opened up, it is good practice to install a gate valve or ball valve on the house side of the tank tee. Make sure the isolation valve is on the house side of the PRV, and never put an isolation valve between the PRV and the pump.
Finally, you will want to install a union at the wellhead to allow the pump to be pulled without having to cut pipe when it comes time to service the pump.
Next month, we will talk about selecting and sizing submersible pump cable. ’Til then .…