water pump

[Ray.Charles]

My wife owns a 3-storey room-for-rent building with water tanks at the ground level, and at the 4th level. The ground level tanks are filled by water from the town supply; then a pump takes the water to the 4th level tank as needed. This pump is switched on triggered by a float at the 4th level.
From the 4th level tank, water is fed to the 1st level by gravity. For supply of water, the rooms at 2nd and the 3rd level are divided into 2 groups, each group consisting of both 2nd level and 3rd level rooms depending on their location in the building. One pump for each group forces water downwards when a fixture calls for it.
This system of activating the pumps on demand worked for about 2 years as designed. But, now the pumps for pushing water down to the 2nd and 3rd level are running continuously without any demand of water from any fixture. WHY? This will ruin the pumps soon besides wasting electricity.
Any thoughts?

[pf-flyer]

Here is a thought. If you could post a schematic drawing of the building plumbing showing how the pumps are connected. That would help. The pump that is running continuously may have an air pocket causing it to lose its prime. I would check the water line that is feeding the pump that is running continuously and make sure that there is an adequate flow of water for the pump to maintain its prime. Is it sucking in air from the supply water line ?

[maxeboy]

What kind of pump(s) are You using. Who is the manufacturer of pump(s)?
Kind regards from
maxeboy

[TicToc]

If not air in the system or a leak, i would check the pressure switch.

[Geoffrey]

Your on-demand water pumps have a pressure switch that turns them on and off. The pressure switch may have a problem. If more than one pump system has this problem, it could be low voltage in your electrical system. These type of pumps have an air tank (or nitrogen or other gas-filled bladder) - an air tank might be full of water. It would need to be drained. Pumps usually come with a user manual. They're pretty decent.

[FrazeeDK]

go to each pump, power them off, pull the cover and you should see two threaded plugs. Pop them and bleed out any air until water comes out then put the plugs back in.. Do to both pumps then repower them and see if they pressure up and shut off.. Also, make sure you don't have some type of cross connect valve that has been opened causing them to run continuously.

[Ray.Charles]

I apologize for taking too long to respond to the very useful posts in the link started by me. The primary reason for the delay was that I wanted to get a better understanding of the problem before I posted again. We still do not have a complete understanding; but, thanks to a 2-person plumbing team we now have a better understanding. Here is an interim report:
The problem was caused by malfunctioning check valves. A check valve is designed to allow water flow in one direction only. At the top (4th) level there are 2 pumps connected to the holding tanks, one each for two separate feeds to the plumbing below in two parts of the building. There is a check valve on the outgoing water flow from each pump. Because of the malfunction, water was flowing back through them creating a local circulatory flow causing the pumps to run continuously. Confusing, isn’t it. Anyway, the check valves have been replaced and the pumps are not running continuously. But, we believe that the pipe layout is flawed which needs to be fixed in the near future.
Thanks for your help and your patience.