Will 50/70 PS give me 7psi over 40/60

[Wolf911]

I'm in the process of installing a iron and carbon backwashing filter and a whole house ro setup. I'm trying to figure out what is the best way to raise my cutin pressure from the well pump so that I always have at least 40psi at the inlet to the ro machine in the house. The well and pump is about 100ft away from the house. There is currently a 40/60 ps at the well house but by the time it reaches the ro inlet at the house a 100ft away I'm only getting 53/33 approx. I need the minimum pressure to be 40psi ,will switching out the 40/60 ps to a 50/70 give me the 7psi on the low end?
I don't need the cutoff any higher than 60psi just to bump up the cutin.
The pump is a goulds 3/4hp in a 135ft well with the water level at 90ft.
I have a goulds v260 pressure tank 84.9gallons.
I tried raising the pressure on the 40/60 a little and it went up to 68 cutoff in the well house and 60psi in the house but the cut in didn't seem to move much approx. 44psi in the well house. I wasn't sure if the 40/60 can be adjusted to accomplish what I want so only tried once.
The feed to the ro is 1.6gpm at minimum 40psi so I don't need much flow.
Will the 50/70ps get me what I need and how much will it lower the 22.8 gal draw down that is currently available at the 40/60 setting. The specs for the tank don't list a 50/70 setting . Is there a formula to calculate this? Thanks for any input?

 

[Bannerman]

what I need and how much will it lower the 22.8 gal draw down that is currently available

The tank specs specify:
31.2 @ 20/40 and 26.2 @ 30/50 = 5 gals difference
26.2@ 30/50 and 22.8 @ 40/60 = 3.4 gals difference
You might then anticipate the drawdown capacity @ 50/70 will be ~20 gallons or ~2.8 gallons less than current.

The tank drawdown capacity specs are based on 20 psi differential so if the cut in pressure is increased without also increasing the cutoff by the same amount to maintain a 20 psi delta, the tank drawdown capacity will be substantially less than specified.

Does your pump have sufficient head capacity to exceed 70 psi cutoff (=161.5') after lifting water 90+ feet from the well?

 

[Sponsor]

 

[Bannerman]

Another option will be to equip your pump system with a Cycle Stop Valve. https://cyclestopvalves.com/

This will allow continued use of the current 40/60 pressure switch settings as any water use over 1 GPM will cause the pump once activated at 40 psi, to consistantly deliver only the actual quantity of water needed at 50 psi continuously.

Although your existing 85 gallon pressure tank may be used with a CSV, because it will fill at only 1 GPM, a 4.5 or 10 gallon pressure tank is typically all that will be needed. A smaller tank is preferred as less water will need to be used before the pressure falls to 40 psi to cause activation of the pump to deluver 50 psi ongoing.

Pumps and Tanks forum moderator Valveman is the developer and manufacturer of CSVs so you may wish to discuss with him the benefits of a CSV for your application.

 

[Wolf911]

I don't know the total head of the pump because I don't know the model of Goulds pump it is. I know it's a 3/4 hp as I saw it going down and that's what I payed for. The well guy that put it in retired after 35 yrs in this area and someone else took over. I contacted him but he doesn't know if he can find the info. Didnt seem like he was going to try to hard either.

With the ps set 40/60 it took 2 minutes 10 sec to fill the tank. When I cranked the switch up it pumped to 68 psi taking roughly 3 minutes 15 sec. I only tried it once though. Seemed like it could have kept going.
How much pressure above 70psi would I need if I wanted to run the 50/70 switch with the 20 psi differential? The pressure relief valve opens at 75psi I believe. Could I set the pressure tank to 48psi air charge and crank the pump up while watching the pressure to see if it develops the 70psi? Does the time it takes to go from 60psi to 70 psi indicate if the pump can handle the higher pressures?

With the aprox. 20 gal drawdown at 50/70 and the normal flowrate of the ro feed rate the well pump should come on only every 12 minutes for roughly 3 to 4 minutes. The pressure tank is new so I want to use it and just a pressure switch if possible.

Also is there some electronics that can keep a pump from destroying itself if any problems occur with the drop pipe (broken pipe, freeze, well water drops etc.)

Thanks[/QUOTE]

 

[Valveman]

Loosen the small adjustment screw in the pressure switch all the way. That will give you the minimum difference between on and off that those switches will do, usually about 17 PSI. Then tighten the large adjustment screw until the on pressure is as high as you want the operating pressure. This way it never gets below a certain pressure.

On for 3-4 minutes and off for 12 is 100 cycles per day. and 36,000 cycles per year. Your pump would last longer running 24 hours a day and just cycling once. Thar is what would happen when using more than 1 GPM if you have a Cycle Stop Valve. The CSV would then hold the pressure at a constant number the entire time the RO is running. No more 50/70 over and over, just a constant 65 PSI for as long as the water is being used. The big tank works fine with a CSV, but you have to wait for the tank to empty as the pressure drops from 70 to 50 before the pump comes on and the CSV starts delivering 65 PSI constant.

 

[Wolf911]

Loosen the small adjustment screw in the pressure switch all the way. That will give you the minimum difference between on and off that those switches will do, usually about 17 PSI. Then tighten the large adjustment screw until the on pressure is as high as you want the operating pressure. This way it never gets below a certain pressure.

On for 3-4 minutes and off for 12 is 100 cycles per day. and 36,000 cycles per year. Your pump would last longer running 24 hours a day and just cycling once. Thar is what would happen when using more than 1 GPM if you have a Cycle Stop Valve. The CSV would then hold the pressure at a constant number the entire time the RO is running. No more 50/70 over and over, just a constant 65 PSI for as long as the water is being used. The big tank works fine with a CSV, but you have to wait for the tank to empty as the pressure drops from 70 to 50 before the pump comes on and the CSV starts delivering 65 PSI constant.

Tanks for the info on adjusting the ps. I'm going to try that and once I get it set ill check the drawdown and see what I have.
Using your example of 17psi difference(after loosing the little screw), if I adjust to 68psi for cutoff I should be around 51psi for cutin. Would I then set the tank air charge to 49psi?
Thanks again.

 

[Valveman]

The specs for the tank don't list a 50/70 setting . Is there a formula to calculate this?

On at 51 and off at 68 would cause a 85 gallon size tank to deliver 17.68 gallons of drawdown. You can run the numbers on this calculator.
https://cyclestopvalves.com/pages/minimum-pump-run-time-calculator

But the draw down would be 17 times more than you need when using a CSV1A Cycle Stop Valve.