Big Pump, A Hill and High Pressure

[Geek]

I have what I think is a bit of a strange application or at least not the norm of what I have read from other sources.  I have irrigation water (not a well but supplied from an irrigation water coop) system where the water comes in  to my property at a lower level than where I need to use the water.  Literally 40 feet of vertical difference between the pump and the demand.  This is the first time I have gotten to play with water pumps and such so have zero experience to fall back on.  We bought this property and needed to get the irrigation system hooked up quickly as it was the only water available during the construction.  Living up to the old adage of “you need it bad – you get it bad”  I went to a plumbing/pump company in town and they told me what I needed as far as pump and such to feed the rainbird system I needed to feed at the site.  The bad news was that I couldn’t get the thing to operate correctly with the pressure switch the way the ‘experts’ had said to do it.  When I started asking questions like “Do I need a pressure tank for this” and saw the deer in the headlight look, I knew I was on my own.  The good news was that I could manually switch the pump on and off and it would work so at least I had water at the site for the fire safety requirements.

So what do I have.  I have a Berkeley B82456-01 jet pump that can do 55GPM and up to 130 psi.  It’s a beast.  What I would like is to have about 80psi at the top of the 40 foot hill (which I think means about 100 psi or so at the pump).  I was looking at the CSV2W 50-120psi version and thought that, along with a pressure tank would be my solution.  Then I saw the 50GPM upper limit on the CSV to which I had my first big question: is my pump too big for the CSV?   Is it more along the line of if I don't actually have a draw of 55 GPM and more like 40 GPM will I be OK with the CSV2W running at 100psi?

What is/was my plan.  Use a pressure switch set to 110 psi with a 20 psi differential set in.  Use a 14 to 20 gal pressure tank rated at 150psi and set the reference pressure on the tank to 88psi.  I used a bit larger tank so that the drawdown on the tank when run at the 100psi pressure was in the 4 GPM range.  So once the demand was removed and the CSV started to fill the tank back up, it had some time to run the pump and not just cycle off immediately.

Does this make any sense?  Am I on the right track or quickly heading out to left field with no mitt?

Any direction you can steer me towards would be most appreciated.

Thank you for your time on this.

Geek

[Cary Austin]

HI Geek
Yeah "deer in the headlights look" is what you get from most pump supply houses these days.  They know enough to get you a price and sell the pump, but they really don't know much else.

According to the curve seen here       https://d1pkofokfruj4.cloudfront.net/media/upload/resource/i/Berkeley-Pumps-SSHM-Series-Self-Priming-Multi-Stage-Specifications.pdf
 
That pump has a max pressure of 108 PSI.  It will only do 55 GPM at 75' or 32 PSI.  That would only be 12 PSI at the top of the hill at 55 GPM.  At 100 PSI at the pump to get 80 at the top, as you have correctly figured, that pump will only deliver 10 GPM.  Can you run your irrigation at 10 GPM?  If so, you can use that pump, but it doesn't give any extra to be able to use it with a CSV.  The best you can do is set the pressure switch for 85/105 and live with the 10 GPM at 80 PSI.

If you can irrigate at 50 PSI, that pump will be working at 70 PSI, and it would deliver 35 GPM.  Then we have enough room to make a CSV work with that pump.  But if you need 80 PSI, 10 GPM is all that pump will do, and a CSV will not help.  Sorry

[Geek]

Cary,

I can live with the 50psi and 35 GPM.  I just have to re-think the number of feeds for each leg of the manifold.  Since I would be running below the 50GPM rating of the CSV2W I would think it would work for this application?  How would you suggest the set up be at the bottom of the hill (i.e. pressure switch setting and tank size to give the pump some time to chill)  Thank you so much for the help here.

Geek

[Cary Austin]

Pumps don't really need to "chill". You don't want the pump cycling on and off when water is being used.  The pump needs to run continuously while any water is being used, then it can "chill" when no water is running.

If you can live with 35 GPM at 50 PSI up top, then you need to run a 60/80 pressure switch and a 70 PSI CSV at the bottom.  The problem is that pump cannot afford any friction loss or reduced pressure fall off as comes with the CSV2W.  The CSV3B2T is a little overkill for that size pump, but that is the reason it won't have the friction loss of the smaller CSV2W.

I would run a CSV3B2T set at 70 PSI, with a 60/80 GHG pressure switch on at least a 44 gallon size tank.  You can go larger with the pressure tank is you want, but the smaller tank will be fine, and it will offset some of the cost of the CSV3B2T which sells for $647.50.

[Geek]

Thank you sir.  One big CSV valve and large tank dialed in.  So appreciate your input on this.

G

[Cary Austin]

You will also want to remove the coil spring from under the bonnet of the CSV3B.  It works fine without it and that cuts the friction loss in half, which would be helpful with a low head pump.