Have a full house cistern with a submersed pump in the bottom of the 3500 gal tank. In the crawl space is a pressure tank with a rubber air bladder and a pressure switch. When I turn on the water it will run normally till (I guess) the tanks water is drawn down (about 5 gallons worth) then it slows down to about a quarter of the stream, and then in about 3 seconds it comes back up to full pressure. With a long shower this will happen several times. My guess is the air bladder has a leak. Any outside chance it could be the pressure switch, or the pump??
Variable pressure from cistern system
- Thread starter Trouthead
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If you have a 20 gallon size pressure tank, 5 gallons of water is all it holds and it sounds like the pump is cycling on/off "normally". Normal on/off cycling causes the pressure to go up and down from 40 to 60 over and over for every 5 gallons used. Adding a Cycle Stop Valve set at 55 PSI will give you strong 55 PSI constant even if you are in the shower for a month. The CSV eliminates the cycles that cause annoying pressure fluctuations and also makes the pump, tank, and everything else last much longer.
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Never heard of a cycle stop valve, but will ask my plumber about it. The funny thing is that my system has been untouched and trouble free for at least 6 years, and never had these pressure and volume fluctuations. Thanks for the info.
Start with the air precharge. Air precharge is always measured with the water pressure near zero. With your jet pump, set the air precharge to 4 or 5 psi below cut-in.
Three seconds is a long time. Maybe it just seems like 3, and its only 1.5.
Seven years is the average life span caused by pumps cycling on and off too much. After 6 years you are starting to see the destruction caused by cycling the pump too much.
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