Question about water pressure drop and how to recover?

ozley · Jul 19, 2016

If turning up your cut off higher check to see if you have a relief valve and its setting. Gone on quite a few weekend call where happy home owners have turn their pressure up and flooded their basements. What is this thing it keeps leaking?

Valveman · Jul 19, 2016

ozley said:
If turning up your cut off higher check to see if you have a relief valve and its setting. Gone on quite a few weekend call where happy home owners have turn their pressure up and flooded their basements. What is this thing it keeps leaking?

Good catch! And most people do not know those little pressure relief valves are adjustable. There is usually a little cap screwed on top that can be taken off, and a screwdriver slot or Allen head wrench is used to tighten the spring and increase the pressure setting so they won't pop off. But they should also be plumbed to a drain or outside so they don't flood the basement if they are needed.

The air charge in the pressure tank also needs to be increased when increasing the pressure switch setting, but it isn't urgent. When you figure out the pressure switch setting you are going to be happy with, increase the air charge in the tank to about 5 PSI less than cut-in.

chopped · Jul 20, 2016

Valveman said:
A submersible well pump can usually supply as much pressure as you need. Like Egon said, just turn up the pressure switch. If you are currently running 40/60 then turn it up to 50/70 and try that. I have lots of customers who run 60/80 or even 80/100 when the house is a long ways from the well and/or up a hill, and/or multi-story. Anything over 55/75 and you will probably need a different pressure switch. The GHG2 is my favorite for higher pressures, like up to 150 PSI.

As you said the problem is most acute when the system is close to cut-in pressure. Adding an additional or large tank will just make the system stay close to cut-in pressure for longer periods of time. The smaller the tank the less time spent close to cut-in pressure. And as usual I am going to mention a Cycle Stop Valve (CSV) as it will solve this problem. Lets say you turn the pressure switch up to 60/80. The cut-in of 60 is still 25% less pressure than when the system is close to the cut-out pressure of 80. With a small tank and a CSV, the pressure will quickly drop to the cut-in pressure. Then the CSV will hold the pressure constant at 75 PSI for as long as you are using water. Only when you turn off the shower and/or all water outlets will the CSV let the tank fill to 80 and the pump shut off. The constant 75 PSI from the CSV will be much stronger shower pressure than an average of 70 PSI, as when the pump is cycling on and off between 60 and 80. Without a CSV the pump will continue to cycle on and off, and much of the time the system will be close to the cut-in pressure, which you already know is when you get the worst/lowest pressure.

Even just adding a CSV to hold a constant 50 PSI for a normal 40/60 system will make the pressure much stronger. Many people think the pressure has been turned up. However, the pressure switch is still at 40/60. The CSV just makes the pressure stronger as it holds a constant 50 PSI, instead of an average 50 PSI, which is what you get when the system continues to cycle on and off from 40 to 60.

Sometimes we do a pump system for multiple houses where the houses are at different elevations. We just set up the CSV and pressure switch to give the house at the highest elevation the pressure it needs, then each lower house has its own pressure reducing valve to knock the pressure down to what they want at that house. For instance we would set the pressure switch for 100/120, which would give a house that is 115' higher a pressure of 50-60. Then houses that are 20' lower than the pump system would have 110 to 130 PSI, which we would reduce with a PRV down to 50-60 as needed. And of course the CSV would hold the pressure constant and not let the pump cycle on/off, no matter which house or how many houses are using water.

Are these the valves you speak of? thanks
Amazon.com: cycle stop valve

Valveman · Jul 20, 2016

chopped said:
Are these the valves you speak of? thanks
Amazon.com: cycle stop valve

Yes but you will get a three year warranty instead of one year if you buy from this site instead.
Constant Pressure Valves and Pump System Monitors – Cycle Stop Valves, Inc

KWRB · Jul 20, 2016

Pressure drop is a function of multiple factors including the diameter of the pipe, the velocity of the fluid, the density of the fluid, and the material (the surface finish of the pipe). Much of the information you're looking for can be found in Crane technical paper 410. There might be a cheap old copy of it online at ebay or something. It's a super valuable resource.

If you're having trouble and want some honest to goodness engineering, let me know via PM and I'll see what I can do.