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I have a 60 yr old gravity fed well that loses its prime after 2 days. The foot valve, wellhead and priming valves have all been replaced and the system was air pressure tested with no drop after approx. 1 hr. Three plumbers have tried to fix it but left scratching their heads.
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Need more info, Please explain what you mean by Gravity Fed Well.
*Whatya gonna do when the well runs dry?Sit on the bank 'n watch the crawdads die.Hey Liz, If I were 60, I'd lose my prime too!Are you in New England...lotsa wells dryin' up this summer.Hope ya didn't go dry...mebee a pinhole !
*The well water level is above the highest outlet and maintains flow by the siphon effect caused by the water running down hill. The plumber is telling me that the air pressure test would find any hole in the system. Would it so easily find a pin hole in a 1" copper pipe buried in wet clay for 60 yrs? the pipe runs about 350 ft down a fairly steep hill. The other thing is the prime didn't last as long after the pressure test, which makes me think it could have made the hole larger. Any ideas anyone?
*Loosing prime after 2 days is a very small leak indeed. How long did the air test take, even if the air was pumped to 100 psi it would still take hours or days for a small leak to show. Where is the foot or check valve? Is it 350 ft away or is it next to your pump?
*Air tests are inherently tricky to interpret. A large volume of air being slowly heated by rising daytime temperatures or by sunshine could mask a slow leak. If the temperature is going up and the pressure is going down, then you know something (i.e. a leak). But if the pressure stays about constant while the air gets warmed, a real leak may not be detected. Conversely, falling temperature can give the appearance of a leak when none exists. When installing solar systems, we'd let the air sit for as long as possible AND track the weather. If we could not explain the results, we started searching for a leak.A hydro test is much more sensitive to small leaks. The loss of a little bit of water from a closed system will cause the pressure to drop a lot. Whereas the loss of a small fraction of compressed air will only result in a small pressure drop.A leak might not be the only cause. Dissolved gasses can come out of solution in the lower pressure region at the top of the siphon. Changes in groundwater levels (any drought in your area?) or usage might change a viable system to a marginal one. A related issue, that you have observed, is that after the pressure test the water in the pipe would have very high dissolved gasses and, in the very short term, might result in losing prime quickly again.The cheapest thing that could reprime the system would be a hand-operated vacuum pump as is used by auto mechanics (about $30). And if you have a small volume to purge, may be the way to go. But every 2 days would be a major pain.If the problem is worse (less time between losing prime) with high flow, that suggests dissolved gasses in the groundwater. If it worse during low flow, it would imply a leak in the piping. -David
*Wow...We have a gravity fed water system that involves a spring and and reservoir. Have learned some things over the years that keep it going. If this system has been working fine and has suddenly started having problems there is a leak or a reduction of water level or flow into the well that lets air in from the well. It will not take much air at all to stop the flow. The air gas thing that David is talking about could be happening but would be an unusual change after 60 years of use. You may very possibly have a leak that leaks with vacumn and not under pressure. Quite often the packing around new adjuster knobs leak. Does the water run constantly at a volume, that does not or may not starve the well, to a resovoir? If it functions by running constantly you may have a problem that is common with spring-resovoir systems. Slight undulations in the pipe will allow air to sit in the high spots. The pressure is taken out by this. The way to deal with this is like a house drain system. Somewhere below the water level of the well stand a vent pipe up to allow enough water far enough down the pipe to clear the vapor lock.
*To answer one of your questions, the water does not run to a reservoir just to the taps and is just an on-demand kind of thing. I am interested by the vacuum leak theory which may explain why the pressure test (60 psi for about an hour, so claims the plumber) did not show a drop. Do you mean for the vent pipe to be installed in the supply line below the water level to act as a sort of self-prime arrangement? And thanks by the way for all of your input.
*Hey...The vent thing would only work with a reservoir type system. You have an interesting system. A 1" pipe that long would have tremendous volume by itself. It could leak a lot of air before a typical guage would know the difference.
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I have a 60 yr old gravity fed well that loses its prime after 2 days. The foot valve, wellhead and priming valves have all been replaced and the system was air pressure tested with no drop after approx. 1 hr. Three plumbers have tried to fix it but left scratching their heads.