I recently installed a 36 gallon well pressure tank with new brass hardware and pressure switch to replace a 24 year old 86 gallon tank that developed a leak. I went with 36 gallons because it's only used for irrigation with 6 zones. I don't know the size of the submersible pump or the depth of the well. The old tank had a 30/50 pump switch but I installed a 40/60 thinking it would improve water pressure. I never notice how frequently the pump cycled with the old tank but with the new one the sprinklers would go for about 1 1/2 minutes and then the pump would run for about 1 minute. Sometimes, the pump would run continuously during the last couple zones. So I replaced the 40/60 switch with a 30/50 thinking it would be less strain on the pump. I adjusted the tank bladder pressure down to 28 PSI. Now, the sprinklers go for 1 minute and the pump runs for 45 seconds in all 6 zones. Is this normal or is this considered short cycling? Thank you in advance!
Well Pump Cycling
- Thread starter LSG
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LLigetfa
DIYer, not in the trades
It is short cycling. Adjust the zones to draw more GPM and consider upping the pressure to 50/70.
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Boycedrilling
In the Trades
Buy and install a Cycle Stop Valve immediately, before you burn up your pump. You have the perfect situation for one.
your other option is to completely eliminate the pressure tank and the pressure switch. Balance your irrigation zones.
your other option is to completely eliminate the pressure tank and the pressure switch. Balance your irrigation zones.
Okay, I believe you but the old system didn't have a Cycle Stop Valve and it lasted 24 years. What's caused the new system to need a CSV? Thanks again.
Boycedrilling
In the Trades
Well if you'd replaced your pressure tank with the same size as your old one you might have been ok. But you didn't. Your 86 gallon tank stored somewhere between 20 to 25 gallons of water. You replaced it with a 36 gallon tank that holds 10 to 14 gallons of water. See the problem??????
Bannerman
Well-Known Member
Mostly, your smaller pressure tank. A tank's size is not determined by what the water will be used for or the size of the family, but is based on the output capacity of the pump. The proper size tank will allow the pump to run for between 60-120 seconds minimum.
Your pump will have a specific delivery rating every time it is running. For example, if the pump delivers 10 gpm but only 6 gpm is being used, then the remaining 4 gpm will enter the pressure tank until the upper pressure switch pressure is attained and the pump is shut down. As water continues to be used, the system pressure will drop again until the pressure switch cut-in pressure is reached and the pump will be activated. This process will be repeated for as long as less than 10 gpm is flowing. This has been the method pumps have been controlled for decades.
A CSV is a newer method to control a pump. In the example above, the CSV will reduce the pump delivery flow rate to match the flow rate of water being used. If only 6 gpm is flowing, then the CSV will limit the pump's output to 6 gpm while also keeping the output pressure consistent. The pump will then not cycle, but will remain operating until less than 1 gpm is flowing. Once less than 1 gpm is flowing, the CSV will limit the pump's flow rate to 1 gpm to fill the pressure tank. Because the pressure tank will only fill at 1 gpm max, only a pressure tank with 1 or 2 gallons fluid capacity can be used to provide 60-120 seconds minimum run time.
The CSV will work fine with the 36 gallon size (8 gallon draw) tank. But you could have done the CSV with an even smaller tank like 4.5 gallon size. The CSV even with a small tank will do a better job than the largest tank you can get.
