cut-in/cut-off pressure 20lbs differnece

ugabulldog · Mar 4, 2011

I am just wondering why it is always suggested to go in twenty lb increments, so as not to have too big of pressure difference? Also, I have a new square D pressure switch, supposedly pre-set at 30-50. Is it possibe that it is a little off, because the cut-off seems a little less than 50. thanks

LLigetfa · Mar 4, 2011

I think there are two reasons for that amount of spread. One is to limit the fluctuation in flow rate at the fixture and the other to limit the amount the bladder has to stretch. It could be the switch is off a tad or it could be that your gauge is off. Compare the water pressure on the gauge to the air pressure on the bladder.

Sponsor · 2022-01-29T12:20:58-0800

ugabulldog · Mar 4, 2011

actually, I have a bladerless tank (yes, rare I know) But I think the cut-off might be low because the pressure gauge on tank shows it cutting off about 46psi, and the drawdown on tank (85 gal) is slightly over 12 gpm, and my pump is 12 gpm so I thought pump would cycle for 1 minute but it is only cycling for 40 seconds.

LLigetfa · Mar 4, 2011

ugabulldog said:
actually, I have a bladerless tank...

the pressure gauge on tank shows it cutting off about 46psi....

I too, have a bladderless tank. It's a precipitation tank for iron removal. I put a shraeder valve on the top of the tank along with another gauge to compare with the gauge next to the switch. I see 2 PSI difference between them.

Do you have a shraeder valve on your tank to check air pressure with a tire gauge? Could be your gauge is off or the switch is off. If you raise your kick-out pressure, the GPM of the pump should drop off a little and you should get closer to a minute or cycle time. Try 40-60 and see how it does.

If I didn't have the issue of my micronizer not working above 40 PSI, I would raise both the kick-in and kick-out much higher just to get more flow on my shower. My 10 GPM pump however is averaging less than 5 GPM so I'm stuck with what I have for now.

ugabulldog · Mar 4, 2011

LLigetfa said:
I too, have a bladderless tank. It's a precipitation tank for iron removal. I put a shraeder valve on the top of the tank along with another gauge to compare with the gauge next to the switch. I see 2 PSI difference between them.

Do you have a shraeder valve on your tank to check air pressure with a tire gauge? Could be your gauge is off or the switch is off. If you raise your kick-out pressure, the GPM of the pump should drop off a little and you should get closer to a minute or cycle time. Try 40-60 and see how it does.

If I didn't have the issue of my micronizer not working above 40 PSI, I would raise both the kick-in and kick-out much higher just to get more flow on my shower. My 10 GPM pump however is averaging less than 5 GPM so I'm stuck with what I have for now.

I also have this setup for iron removal with an air injector. i put a schrader valve on my air control valve. I don't have a pressure gauge next to switch, only on tank.

Texas Wellman · Mar 4, 2011

I set them up all the time for 30-60. Regular galvanized tanks are the norm here because bladder tanks can amplify odors in the water. With a 30-60 differential and a good air charge on that "bladderless" tank it is not unusual to almost double the drawdown and extend the time between air charges. I typically add air to my system 2-3 times per year.

ugabulldog · Mar 4, 2011

thanks Texas, how do I know if I need to add air to tank?

Texas Wellman · Mar 5, 2011

Wait for a hot summer day or a cool winter day and feel the tank. You'll quickly know where the water line is. Charge that sucker up until air comes out of an open spigot and then close the spit and charge some more. Get it about 1/2 air/water. It will last a long time like that and will perform as well as a bladder tank for a few months.

Good luck.

Cacher_Chick · Mar 5, 2011

Actually you never need to pump air into the system with a non-bladder tank. If you drain all of the water from the tank and then turn the pump back on and allow it to fill, the air charge will be at the proper level. For homes that do not use an airmaker bleeder or snifter valve setup with an AVC, this should be done every couple of months.

Texas Wellman · Mar 6, 2011

Yes, and if you add an air charge the tank will perform even better, rivaling the capacity of bladder tanks. I do not like bleeders or AVC's. AVC's tend to fail quickly in these parts and bleeders make the well nasty (aerated water in the top of the well). I will install them if I think the homeowner does not keep their system up but on my own I prefer not to use them.

LLigetfa · Mar 6, 2011

Texas Wellman said:
Yes, and if you add an air charge the tank will perform even better, rivaling the capacity of bladder tanks..

Agreed. There is this thing called Boyle's law that states that for a fixed amount of air kept at a fixed temperature, pressure and volume are inversely proportional, meaning that while one doubles, the other halves. The small amount of air trapped by simply draining the tank is fairly quickly absorbed into the water resulting in diminished draw down resulting in sooner waterlogging. Using the same concept of precharged bladder tanks, filling it with compressed air results in more draw down and longer time to waterlog.

One trick on galvanized tanks to see the level quickly, is to warm the side of the tank with a propane torch. The water will resist the heating and show as condensate from the torch.

cut-in/cut-off pressure 20lbs differnece

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