When well water pump switch goes on-off every few seconds what is the cause?

Answer 1

The cause is a pressure tank that has lost it's residual air (called 'waterlogged '). The tank is now full of water and every time you need water , the pump has to switch on to provide it. - You may be able to fix this if you are handy with tools and have a small compressor. Here is an article I wrote on this -

Well pressure tank This tank where the water enters from the pump is a critical part of your system . It should have an 'air charge' of approximately 27-28 psi if the pressure switch is a standard 30/50 switch. (see note below about 40/60) If this air charge has gone down, then your water pressure will be lower. If this tank is very old, possibly silver or green in color, then it's a "galvanised tank" and is 'waterlogged'. This means you have to recharge the air with a compressor (just like blowing up an auto tire) To do this, switch off the pump. Open a faucet near the tank and let most of the water out. When you think it's nearly empty, close the valve to house and pump in with the compressor till the needle on your tank gauge points to 27, 28 psi. Now switch on the pump and the pressure should be improved. -IF your tank is a pale blue one, then chances are it's a 'bladder' tank and low pressure means your bladder is leaking. -You can pump it just as I said already, but in this case it will only last 2-3 months. You basically need a new tank.

In all cases check the size of the pressure switch. It's printed somewhere on it . 30/50 as I've mentioned is common but some are 40/60. In this case pump in 38 psi of air. Both pressure switches are adjustable to a small degree by turning the central spring up or down. It's essential that lower limit of this switch is 2-3 psi above residual air pressure.

Always use a good round tire pressure gauge, (available in auto stores for about $5.) to check tank air pressure, Don't rely on the installed gauge, they soon get erratic.