Monday, June 7, 2010

Water pump coming on too often or taking too long to come on

If you live in Trinidad, you probably know about water problems. A water pump to feed an average house is at least $1500 TTD now. Calling a plumber of electrician is costly and you can do simple checks to fix a pump yourself. This article deals with a pump equipped with a pressure tank and pressure control switch, not with a smart head (a cone shaped attachment).

For info on a smart head pump TRY HERE.


Pressure tank vs. smart head
If you are considering buying a new pump, I recommend getting a pump with a pressure tank, it comes on less frequently and has pressure stored and waiting for you to use. This pump only comes on when the reserve in the tank is used.
The smart head pumps usually suffer from a lag where after you open a faucet/tap you get low pressure then a few seconds later the pump comes on. This is annoying and means that a pump would be running the whole time a tap is open! Imagine the pump running for the whole time you are in the shower vs a few times on and off! The smart head changes the rpm of the pump according to the needs at any point in time.A faster RPM would give a higher pressure in the line.
Both types will eventually get noisier as the bearings go bad and need to be replaced. In most parts of Trinidad and Tobago this is about three years after getting a new pump/bearings, if being used continuously.


Before doing work on your pump disconnect the power and shut off both the inlet and outlet pipes. Have something ready to collect water because there will water stored in the pump.

If you have problems with your pump it is usually one of two things: the pressure tank, or the pressure control switch.

You can get a pump now that has a smart head which replaces the pressure tank and switch. The pressure tank consists of a metal outer case and an inner bladder/diaphragm (balloon). It works by having water pushed into the diaphragm and the diaphragm expands to occupy the case and stores high pressure water in it. The diaphragm contracts to release water into the house's plumbing system. The switch tells the pump to come on if the pressure is below a minimum pressure and to stop running when a certain cutoff pressure is reached on the pump's outlet pipe.

Pump coming on and off very frequently
If your pump trips on and off rapidly, say once every 10 seconds or worse every 3 seconds and there is no open tap the problem is the pressure tank (The float on a toilet was broken and water kept filling into a toilet which made the pump run continuously and I had to figure out it was the float and not the pump to be fixed).
The tank has a standard air valve on the top which needs to have about 20 psi in it. Just checking the pressure releases a significant amount of pressure from it so keep that in mind when measuring it. Use an air pressure gauge to see if there is sufficient pressure in the tank. If it is low them pump it up.

The diaphragm can burst and so no pressure is kept in the tank as the tank becomes filled and does not empty. The switch tries to maintain the high pressure so with any slight leak the pressure drops to below the cutoff and the pump comes on to build it back up. This process happens very quickly so you will hear the pump going on and off rapidly. The tank then has to be changed by unscrewing it. If the pump is not securely bolted to the ground then I advise you disconnect the pump from plumbing before you attempt to unscrew the tank. Putting pressure on plumbing can break pipes and joints and crack old glue which will cause leaks and give you extra work to fix later. Ideally you should already have a union on the inlet and outlet pipes, if not now is a good time to put it in. One person can hold the pump and the other can turn out the tank. A WellXtroll two gallon tank is about $450 TTD. Remember to use thread seal tape on the tank. Another (more thorough) explanation is found here.

Pump taking a long time to come on
If your pump takes a long time to come on after if has released the stored water then it is probably a pressure control switch problem. It is rare for a pressure control switch to die. In Trinidad we get dirty water often and there can be large particles of sediment, or rust from inside the pump in the small opening going to the switch. These particles stick to all plumbing internals and encourage rusting and clogging. The outlet hole where the switch attaches to the pump is small and can become blocked. The space and pad that detects the pressure change can also become clogged and not detect the pressure as it appears in the rest of the system. If the hole is almost completely blocked it takes longer for the switch to detect low pressure in the line. This is most annoying when you are in the shower and have to wait a minute for the pump to trip on to give you water. The switch can be unscrewed (after disconnecting wires to it) from the body of the pump and cleaned out. You may need to remove inlet or outlet piping to allow the switch to spin out depending on your pump setup. I have seen both male and female ends for the switch to the pump body. The male end was a plastic head which cracked when I overtightened one of the 6 screws on it. There was a very slight leak because of this. The female end had a metal head so it could not crack but over tightening would damage the threading which you do not want either. Do not forget thread seal tape on the switch when reinstalling it after cleaning.

Pump running continuously but not pumping water
If the pump runs continuously and there is no water being pumped out there may be air it. Switch off/unplug the pump. If you have a union close by on the outlet line of the pump, open it a couple turns water starts to flow through. You can just loosen it with two or three turns instead of taking the collar completely off. Once a constant stream of water starts to come out you can tighten the union. There is an O-ring that can come loose inside the union. If water leaks when you retighten the union the O-ring is probably out of place. Take the collar completely off the union and reseat the O-ring.

If you do not have a union, there is a air bleed screw somewhere on the top of the pump. Loosen the screw a couple turns until you hear the air coming out then tighten after all the air comes out and water starts leaking out. Switch on the pump and the pressure should start to build in the line now.

Testing the pump
When the pump is ready to be tested, first open the valves to run water through the pump before you power it on. The pump should never run dry, water lubricates and cools it. Stand by the power switch and valves to shut off if something is wrong. The first time the pump runs there will be air in the tank which will be corrected the first time a tap is opened. Check all joints for leaks. Slight PVC joint leaks can usually be fixed by applying PVC glue to the joint and letting it dry.

If the pump does not come on when you power it on you may hear a hum coming from it or nothing at all. If there is a hum and the shaft/fins are not spinning, it has ceased up. Unplug it and use an appropriate screw driver to turn the shaft. It should be moving smoothly. If you hear nothing there is probably no power getting to the pump. Ensure the outlet has power to it, check the breaker panel to see if it tripped and finally double check the wiring in the pressure control switch.

Lastly, you should be aware of how your pump sounds. If it was quieter and had gotten louder this is a sign that the inner bearings are failing. They can be changed but it requires completely stripping the pump by a professional.

Tips: - Do not leave the pump on unnecessarily, switch it off when going to bed or when leaving the house. This extends the life of the pump and saves electricity.
- Reduce the cut off pressure (keep the same cut on pressure) of the pump by adjusting the appropriate screws on the pressure control switch. This saves water by having less wastage on taps and the pump also runs less to reach the lower cut off pressure.
- Tighten valves under on sinks or hoses so that a lower pressure comes out even if the tap is opened all the way. This saves water and will even money when the pump is run for less time.

2 comments:

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  2. water pump hums like it is trying to start, and doesn't, them after a few times it runs. after awhile it hums again.
    any idea what the problem may be?

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