Submersible pump accessories are the plumbing and electrical components of a pumped water system that is particular to a submersible pump system vs. a jet pump system. For simplicity’s sake. We will divide them into two categories – down-hole accessories, and aboveground accessories. The down-hole accessories are the check valves that we talked about in the April article, as well as torque arrestors, cable guards, drop pipe, pitless adapters, pump cable, splice kits, etc. We will cover the torque arrestors, cable guards, and drop pipe this month, and the rest of the down-hole accessories in the coming months.
Torque Arrestors
A torque arrestor is a rubber or flexible PVC device that mounts on the drop pipe a few feet above the pump to prevent the pump from rotating due to start-up torque. They also center the pump in the well casing. Torque arrestors are mandatory when using PVC or poly drop pipe and often used with steel drop pipe as well. They look like a 2-foot piece of 2-inch radiator hose with four longitudinal slits running most of their length. They are installed using stainless steel hose clamps, and the ends are pushed toward each other, forcing the center section to bulge out to make contact with the inside of the well casing.
Cable Guards
These are inexpensive molded plastic or rubber devices that slip over or snap onto the drop pipe. Centering it in the good casing to prevent the drop pipe from trapping the pump cable against the well casing, abrading it. They always should be used when the drop pipe and well casing are steel since steel surfaces can become very abrasive as they rust and corrode with time. Many installers use them with plastic well casing and drop pipe as well because they make a nice, clean installation.
Coupling in-between the cable guards
They should install on every other joint or about every 40 feet. The pump cable should stretch tight. And with electrical tape. Taped to the drop pipe adjacent to both sides of each cable guard, and at each coupling in-between the cable guards.
Drop Pipe
Drop pipe is the name given to the pipe that runs down inside the well from the wellhead to the submersible pump. Drop pipe can be made from any material suitable for transporting the pumped fluid that can support its own weight, plus the weight of the pump. There are three types of drop pipe commonly used in submersible systems – galvanized steel, PVC, and polyethylene.
Prop pipe Plastic
Plastic drop pipe can be used in most residential applications and is preferred by many installers because it is lighter, easier to handle, and it resists corrosion. The three most common types of plastic drop used today are threaded schedule 80 PVC, threaded schedule PVC, and high-density polyethylene HDPE.
PVC Pipe
Early attempts to use PVC pipe for drop pipe involved the use of schedule 40 PVC sprinkler pipe. Either glued together or by gluing on male and female adapters and screwing them together. It is cheaper than threaded schedule 80 and 40 PVC drop pipe, but the potential strength problems well outweigh the savings.
Schedule 40
Threaded schedule 40 and schedule 130 PVC drop pipe comes in 20-foot lengths; it has male pipe threads on both ends and can be connected with couplings, or threaded check valves. There are limitations to the amount of weight that can be supported by any drop pipe. And also as you might guess, plastic carries less weight than steel.
HP limitations
Table 1 shows one manufacturer’s depth and HP limitations for the four most popular sizes of its threaded drop pipe. The depth numbers on this chart are for a 30/50 pressure switch. And are included for illustration purposes only – they may be different from those for the pipe you are using. Ask your pipe supplier for a chart on its PVC drop pipe before deciding to use it for settings deeper than 300 feet.
Couplings
Most installers use either plastic or stainless steel drop pipe couplings with PVC drop pipe. Brass and galvanized couplings also are available. If choosing brass, make sure it is no-lead brass. Galvanized couplings are OK if they are specifically designed for use with drop pipe, and have the long, tapered entry that facilitates assembly.
Plastic drop pipe couplings
Plastic drop pipe couplings must the extrude and machined type. As opposed to the injection-molded type. Never use molded couplings to connect PVC drop pipe unless you need practice fishing for a lost pump in the bottom of a well. They fine for light-duty aboveground applications but do not hold up well under the stresses encounter in a drop pipe application. They crack easily and can fail. Causing the drop pipe string and the pump to fall to the bottom of the well. In fact, most cPVC Pipes manufacturers void their pipe warranties if molded couplings are used.
Schedule 80
The machined PVC couplings are available in schedule 80 and schedule 120. I have never seen a broken machined schedule 80 PVC coupling, but many installers go the slight extra expense of using schedule 120 couplings for the added safety margin. Since they only are a little bit more expensive, the scheduled 130 couplings probably are worth it. Just for the peace of mind.
Manufacturer’s pressure ratings
There is an adequate safety margin in the manufacturer’s pressure ratings so you can choose pipe with a pressure rating just large enough to do the job without having to worry about overstressing it.
Poly drop pipe connections
Poly drop pipe connections make using insert fittings that inserted into the inside of the drop pipe. Insert fittings are available in a number of configurations to connect the poly to itself and to threaded fittings. They are held in place with stainless steel hose clamps. In good applications, use two stainless steel clamps on each side of each fitting.
Plastic insert fittings
Fittings are made from galvanized steel, stainless steel, brass, and plastic. If brass fittings are used, make sure they are no-lead brass. Plastic insert fittings are not recommended for connecting drop pipes for water well applications because of strength considerations.
Galvanized steel drop pipe
Galvanized steel drop pipe still is preferred by many pump installers, but, like plastic, it has limitations. The Difficulty in handling. And rust and corrosion are the two main reasons for the increasing popularity of plastic. Except in the deeper applications. Where the strength of steel is needed just to hold the weight of the drop pipe. Pump cable, water, and pump.
Steel drop pipe
Steel drop pipe is shipped with a coupling on one end. Which used to make the connections. Except when a check valve is required – every 200 feet, as outlined last month. In which case a malleable iron check valve should use. Many installers use no-lead brass or stainless steel check valves on galvanized steel drop pipes. But I don’t recommend it because these dissimilar materials have the potential to cause galvanic corrosion, which can attack the steel drop pipe. Causing the threads to fail, and allowing the pipe, wire, and pump to drop to the bottom of the well.
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