Two wells on one pressure tank

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raceman17

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Hello,
I have an issue with water hammering that is getting the best of me.. I will try my best to describe my setup.

First well was installed 8 months ago like an everyday well. Check valve at the pump, check valve before the pressure tank and then a 40/60 switch at the 30 gallon pressure tank. This well feeds my sprinkler system only. The issue I had or the issue I made was that it just took hours to water all my grass. I have alot of grass and the sprinklers would run from 2am until around 12pm. So I figured I could put another well in and double my gpm for my system. The one well was running on an average of 12 gpm.

So a few weeks ago I put in a seperate well. This well is approximately 70 feet away from the first well. My setup on the second well is a check valve at the pump and then at the top of the well I have a pressure switch. The 2nd well is tied in to the sprinkler system right before the master valve. The mater valve is roughly 30 feet give or take a few feet from each well. It kinda centered between the wells. I added a tee to the 1" line and both wells are feeding into the 1 mater valve thru 1" pvc and then the water is distributed through the valve manifold. Everytime the 2nd pump turns off (once the zone is complete) there is water hammer and the 2nd pressure switch cycles 5 times or so rapidly before it cuts off. When the zone come on the 2nd pressure switch just continues to rapidly cycle of and on until i manually close the switch contacts. At the point the two wells work togther and produce around 20 gpm running a pressure of 50psi or so.

I initially thought I have a bad check valve in the 2nd well at the pump so I pulled it this evening and installed a better quality flowmatic check valve at the pump. This did not fix the issue. I also added a small water hammer arrestor at the 2nd well pressure switch manifold. This didn't seem to help either. The first well which has the pressure tank right at the point where the well is drilled is working how it's suppose to work. No water hammer on that well and the pressure switch cuts off and on at 40/60. The 2nd well has no pressure tank but only a pressure switch. The flow rate of my system once everything is turned on has both pumps running at the same time and the pressure in the lines are around 50psi. The 2nd pump is not short cycling because of excessive pressure built up in the system. Each zone is calibrated to run at 20gpm and 50 psi. I also bought a new pressure switch but haven't installed it. The pressure switch and check valve on the 2nd well is new also. Any suggestions on what I can do to get this system running. Is my only option installing a 2nd pressure tank at the 2nd well? If possible, I would not want to add this tank is there are inherent options. If a smaller 2gallon pressure tank would help at the 2nd well I would be ok with that. The location of the 2nd well just isn't in the right place to install a big pressure tank if I don't have to.

Any help would be greatly appreciated.

Thanks
 

Valveman

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Pressure switches must be very close to the pressure tank. You might be able to add a small pressure tank on the same tee as the pressure switch and stop the bouncing. Sometimes it works, sometimes it doesn't. Depends on how much friction loss there is between the pressure switch/little tank and the big tank. You could also move the pressure switch for the new well over to the big pressure tank. The extra check valves at the top of the well are also part of the problem. They will perpetuate the bounding of the pressure switches. But mostly, the second check valves by themselves can cause water hammer and switch bouncing on pump start, as well as negative line pressure that can draw contamination into your water supply. There should never be any other check valves in a system except the one down on the pump.

Ideally a Cycle Stop Valve on each pump would give you a mechanical soft start and stop, eliminate the need for a large pressure tank, and allow you to match the sprinkler zones to the yard and not the pumps. The primary pump set for 50/70 pressure and the secondary set at 40/60 means only one pump will run when only one pump is needed. But the backup pump will automatically come on when the primary pump cannot keep the pressure above 40 PSI.

Two Subs same system plain (1).jpg
 

raceman17

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Pressure switches must be very close to the pressure tank. You might be able to add a small pressure tank on the same tee as the pressure switch and stop the bouncing. Sometimes it works, sometimes it doesn't. Depends on how much friction loss there is between the pressure switch/little tank and the big tank. You could also move the pressure switch for the new well over to the big pressure tank. The extra check valves at the top of the well are also part of the problem. They will perpetuate the bounding of the pressure switches. But mostly, the second check valves by themselves can cause water hammer and switch bouncing on pump start, as well as negative line pressure that can draw contamination into your water supply. There should never be any other check valves in a system except the one down on the pump.

Ideally a Cycle Stop Valve on each pump would give you a mechanical soft start and stop, eliminate the need for a large pressure tank, and allow you to match the sprinkler zones to the yard and not the pumps. The primary pump set for 50/70 pressure and the secondary set at 40/60 means only one pump will run when only one pump is needed. But the backup pump will automatically come on when the primary pump cannot keep the pressure above 40 PSI.

View attachment 94809
Thank you for the information. The first well is the only well thay has the two check valves. I only installed the one at the top of the well because that was how alot of systems I looked at on the internet were set up.
I will look into a CSV as well.
Last night as I'm racking my brain thinking of a solution I thought of using a 24 volt contactor to turn on the 2nd pump. My first well is a 110 volt pump. I can come from the output of the pressure switch with 110volt control wires into a small 24volt transformer and then this transform can send 24volts to the contactor to switch on the pump. The new pump is 240 volt. The location of thr wells would make this a pretty easy install. I thought about using a 110volt coil contactor but figured the 24 volt would be safer. Thoughts?
 

raceman17

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I went over my system this morning a realized that my irrigation controller operates each valves from a 24 volt signal. So I threw togther a mockup of the contactor so it would operate once the master valve was triggered. The coil energizes and closes the contactor. I crudely hooked up a contactor to the irrigation controller and everything works as expected. So now, as soon as the sprinkler system is turned on, the 2nd well kicks on... the pressure isnthe system drops to below 40 psi and then the first pump kicks on with the pressure switch and the system stabilizes at 50 psi. I this a viable solution?
 

Valveman

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There are many drawbacks for using a pump start relay compared to a pressure switch. But it will work. Just make sure you have a 75 PSI relief valve somewhere in case the pump start relay starts the pump when no sprinklers come up.
 

raceman17

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There are many drawbacks for using a pump start relay compared to a pressure switch. But it will work. Just make sure you have a 75 PSI relief valve somewhere in case the pump start relay starts the pump when no sprinklers come up.
There is a 75psi relief valve on the first well so that should protect it. How I have it wired is that the 2nd pump will only kick on when the mater valve is activated so there is no way the 2nd well could kick on unless the irrigation system is running. Also, having the 2nd well tied to the master valves let's me keep all my hose bibs running on the original well using the pressure tank for when there is a demand for water.
 
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