Are foot valves prone to stick shut randomly?

[MillWeld]

That's the only answer to my problem I can come up with.
I am pumping from a rainwater cistern 5' deep to a pressure tank for watering a garden. Pump is set to cut in at 30 psi and out at 50. Cistern does have fine sediment in the bottom so I have inserted the dip tube/footvalve assembly in a 4" perforated plastic pipe wrapped with a sediment sock to act as a filter to minimize sucking up sediment.

Here's what happens:
When the pressure reaches 50 the pump cuts off as it should. When the pressure falls to 30 the pump cuts on also as it should BUT sometimes it does not pump water even though it is running. (The housing will eventually get warm if left running too long.) It may go through 6 or 7 on/off cycles successfully and then fail to pump water the next time the pump cuts in. Sometimes it is just 1 to 2 cycles before failure. I can use it only if I am present to tend it.

I have a filter between the pump and pressure tank and pressure gauges on both sides of the filter that read the same pressure so I know the filter is not clogged. I have removed the footvalve many times and when I turn it upside down I hear a click indicating it opens and closes. I have spent so much money and time to get this working it would have been cheaper to water the garden with bottled water. Help!

 

[Stihlrunner]

I haven't had a problem with foot valves sticking closed but I've had problem with sediment keeping them from closing. After a day or so the pump loses prime and just runs and runs.

Sounds like you need to check all your connections for possibly sucking air.

 

[MillWeld]

I have checked connections - even dug up the line to do so and could not find a leak source. Could an air leak behave randomly as I have observed? I have turned off the pump at 50psi and the pressure held constant indefinitely.

 

[DFB]

I would try a new foot valve then

Are you sure that the pickup is always in the water and does the recovery rate keep up with the draw? I had a problem like that once two of us were on the same well but the neighbors pickup was lower. Neighbor still had water but my system was sucking air.

 

[MillWeld]

The valve is in at least 4 feet in the water. It takes about 5 minutes to charge the tank (which has a 5 gal drawdown) from 30 to 50 psi. (I think that is pretty slow. It is an obsolete 1/2HP Waterace centrifugal pump purchased at the Surplus center 3 years ago.)
Takes about 15 minutes 'empty' the tank.

 

[MillWeld]

Problem solved! The clue to the solution to my problem was in the original observations.

I have removed the footvalve many times and when I turn it upside down I hear a click indicating it opens and closes. Help!

This footvalve should not "click" when inverted. The valve is spring-loaded and should be silent. I was curious as to what the click was so I looked very closely thru the perforated strainer and saw a small part rattling around. I dissambled it and found a loose nut which is suppose to maintain spring tension on the seal when the pump is off. When the pump is on the suction opens the seal against the spring pressure.

Thanks to DFB for suggestion a new footvalve. Got me moving in the right direction so I could repair the old one.

I have had so many problems with this system (detailed in earlier posts) but now I think I'm good to go.:cool2:
Bob

 

[DFB]

That's great for you were able to repair it and at no cost!

 

[MillWeld]

Right! Repair at no cost is a victory.
Bob

 

[RobertBrown]

I must be missing something because still don't see how that would starve the pump. I could see where it would not allow the pump to shut off or short cycle.
I think you may have more than one issue but it's hard to say with knowing how your system is plumbed. Perhaps the nut was obstructing the waterway and starving the pump?.....obviously it is trapped in the valve so that it cannot be sucked into the impeller. What size is the foot valve?

 

[MillWeld]

I have a hard time understanding too. The spring actually keeps the valve shut tighter, so it is anti-intuitive. I'm so glad to finally have it working I am not trying to seek an explanation of it, although I would like to have one. It fits a 1" dia pipe.