I have a swing check valve that is between the water meter and the main ball valve. I have a water pressure booster and noticed that when no faucet is open in the house the pressure drops slowly, making it hard to maintain water pressure. I've tested by turning on the pressure booster with 4 gallon pressure tank and closing the main ball valve. The water pressure held. As soon as I opened the main ball valve the pressure started to drop.

I opened the top nut on the swing check valve and tried cleaning with a tooth brush what I could. The valve does not seem to be corroded since it had been installed 2 years ago and moved pretty freely. After closing everything back up, it's the same. The pressure gradually starts lowering.

My utility water pressure is at 10 PSI and they won't do anything to increase it.

I wouldn't even know how to take it out since it is inside a circular irrigation box surrounded by concrete flooring.

main water valve

water utility pressure


Swing-check valves (actually, all check valves) rely on back-pressure to seal, and the more back-pressure the tighter the seal.

NO check valves should be considered totally fluid-tight; some backflow should always be expected.

Your swing-check probably has a rubber (or other elastic material) seal which could be worn or damaged (accentuating the leak-by), but 2 years does not seem old enough for normal use to cause that. What did you find when you opened it up?

It is interesting because one would assume that high differential pressure (i.e. high pumped pressure on your side vs. low-10 p.s.i.-pressure on the service side) would proportionally improve the tightness of the check valve's elastomeric seal... BUT, there is also the fact that the normal leak-by rate would proportionally increase if the downstream pressure is significantly higher than that upstream (high D/P).

Maybe research if better quality industrial-grade check valves can be procured in your area before making a difficult swap. Maybe consider double check-valve setup (I have seen this where critical utility service had danger of contamination).

  • When I opened the top nut, I just found a bit of dirt. Couldn't open the flapper past 90 degrees to check the seal. – Rick Oct 24 '20 at 23:04
  • You should be able to pull the clapper all the way out of the valve from the top, and replace the gasket if necessary. Find the brand and model on the valve body and research the specs... I hope it isn't a cheap import... – Jimmy Fix-it Oct 25 '20 at 4:47
  • I got the guys that installed it 2 years ago to come back and verify. They managed to take the clapper out and cleaned it, but still was loosing pressure. They told me that I would need to get a spring check valve, but in the process would need to get into the concrete to replace. They told me that it is probably due to the hard water here. – Rick Oct 27 '20 at 23:52
  • The guys that installed it two years ago came by to check on it. They managed to pull out the clapper and tried to clean it with same results after putting it back together. The only markings I saw was LF. They told me that they would need to replace the swing valve with a check valve, which involves making a hole in the concrete driveway again. They blamed it on the hard water. – Rick Oct 28 '20 at 2:20
  • Got some help removing the clapper. It was cleaned and put back together, but it still leaking pressure. They say I have hard water and that might be the culprit. – Rick Oct 29 '20 at 0:47

If you turned off the incoming valve when the pressure is high, does the pressure hold or does it fall? If the pressure holds at the higher reading, the check valve is at fault. instead of trying to fix that check valve since if you break it the cost to replace may be extreme, why not just add another good "Made in the USA" check valve at the inlet to the booster or between the booster and this check valve?

  • When I turn the booster on and set to 65 PSI and close the main ball valve that is after the swing check valve, the pressure holds. As soon as I open the valve the pressure starts to drop. When I leave the booster on it keeps turning back on every 45 second since the pressure keeps dropping even though no faucets have been open. – Rick Oct 25 '20 at 12:04
  • It is pretty inaccessible to tap between the main valve (concrete driveway) and the concrete house. So I depend on the swing check valve. I have my pressure booster inlet from a toilet inlet valve that I had put in a T and the output to a cold side water heater line. Both sides have spring check valves. The problem with this setup is that I can't leave the output of the pump wide open since it never really creates sufficient pressure. I have to open the ball valve about 1/4 of the way so it creates pressure slowly. Sometimes it's too slow since the swing valve seems to be open. – Rick Oct 25 '20 at 12:14

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