Author Topic: Pump Selection  (Read 107 times)


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Pump Selection
« on: June 13, 2017, 12:04:44 PM »
Last year I installed a new irrigation system that has a demand of about 7GPM/zone.  What happens when I try to run it is that after a (short) while it loses pressure and crashes.  I figured I just needed to add a larger capacity pump, but my recent research has lead me to believe I need a CSV, so I actually purchased a CSV1A which I plan to install this weekend. The resources in this forum have been amazingly helpful.

I'm not sure that will solve my GPM problem but I'm going to do it anyhow as it makes soooo much sense.

About a year ago my expansion tank bladder went and I had a new tank, pressure switch, manifold, water softener, filter, etc. installed so I'll be adding the CSV just in front of that. Off the top of my head I'm not sure what the capacity of the tank is but it's about 3-4ft tall and 2ft wide. I had a tankless water heater installed around the same time too.

The plumber told me my pump would only produce about 4.5 GPM when he installed the new equipment.  He suggested a variable speed pump that would give me up to 12 GPM. Clearly, given the CSV I'm not in the market for a variable speed pump anymore. 😊

I'm looking at pumps, specifically the Lancasters.  I'd like to maintain 55 PSI if I can (I think my switch is 40/60).

When I look at the T-Series spec sheet, I see that the various pumps operate most efficiently at certain depths. For example a 1/2HP pump operating at 80ft and 50 PSI would be far more efficient than a 1HP pump operating at the same depth. I think being able to pump 10 GPM would be adequate for my general needs, even with irrigation and a shower running at the same time.

I don’t know the depth of my well!! I went to the town hall and there’s no record of it either.

I back on to wetlands and doubt my well is all that deep, but you never know.

Should I check well depth and depth to water before I size a pump, should I pull my pump first, or should I go with what makes logical sense which would be a 3/4HP pump?  Am I going in the right direction with Lancaster which seems to use good componentry?

I was going to order the pump ready for the weekend, if it turns out I don’t even needed after I get the CSV set up, I can always return it.

Please bare in mine, I’m not a plumber so take it easy on my dumb questions.


Cary Austin

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Re: Pump Selection
« Reply #1 on: June 13, 2017, 01:16:03 PM »
If the pump only makes 4.5 GPM and you are trying to irrigate at 7 GPM, that is what causes the pressure to fall off.  A CSv can't help with a pump that is too small.  You really do need to know the depth to water in the well to correctly size a pump.  But a CSV will allow you to install as large a pump as you want, and the CSV will make it work at smaller flow rates as needed.

You also need to make sure the well will produce 7+ GPM.  If the pump you have will produce 4.5 GPM at pressure, it may put out 7-8 GPM without pressure.  i would run a pipe wide open and do a bucket test on the well.