water tank////PSI

[steve t]

2 questions,,,,,,why does my hot water tank sound like it got air in it when taking a shower, it rumbles, also my pump water psi drops when pump comes on for a few sec, then goes back to normal, i have a baldder tank 25 gal

[LazyPup]

You pump is controlled by a pressure switch which is set for a "Cut in" (start pressure) and "Cut out" (stop pressure).

That slight pressure drop that you are seeing is nothing to worry about and it will have absolutely no effect on the performance of your fixtures.

Once the pump starts it will continue to run until the pressure in the tank reaches the Cut out pressure. As long as there is no water consumption the pressure in the tank should remain constant however as water is consumed the volume of water in the tank decreases, which allows the compressed air in the tank to expand and the pressure of the compressed air will decrease proportionally. When the pressure has dropped to the Cut In pressure the pressure control signals the pump to start however there will be a few moments delay while the pump starts and the water actually begins to flow into the tank from the well. During those few moments the water flow which initially triggered the start continues and the pressure continues to drop momentarily until the pump is fully engaged. Once the pump is up to speed and water is flowing the pump should be able to maintain the pressure at a constant pressure or possibly increase the pressure slightly, depending upon the volume of the demand. Once the pump has moved a sufficient volume of water to increase the pressure of the compressed air in the tank to the cut out point the pump will stop.

A knocking or rumbling sound in a water heater is usually associated with gas water heaters that have a considerable amount of mineral scale built up on the inside of the tank. It results from not periodically flushing the tank as recommended by the MFG, however once the knocking sound is present simply flushing the tank will not alleviate it because the scale has by now cooked into a hard lump that will not flush out. It is generally a sign that the tank is nearing the end of its useful service life.