Water Tank Air Pre-Charge Pressure Q&A#3

What's the right air pressure setting for water tanks
Tank pressure climbs above the pre-charge psi

Normal Water Pressures in a Water Pressure Tank are Above the Air Pre-Charge PSI

After the pump ran the pressure in my water tank was higher than the pre-set pressure: is that OK?

I put 28 psi in my water tank then when I let it fill with water the pressure reading was higher. Is this normal? On 2019-02-09 by Donald R Bryant

by (mod) - Yes, it's normal for the pressure reading in the tank to go up as the pump runs

Thanks for asking Donald.

Yes it's normal for the pressure reading in the tank to go up.

The 28 lb that you put is the correct air pre-charge for a pressure control switch with a CUT-IN pressure of 30 PSI.

But of course when you're pump runs it's going to raise the pressure up to whatever is the CUT-OFF pressure set on your pressure control switch.

If your pressure switch is factory set to 30/50 that's a CUT-IN of 30 psi (for which 28 psi is the right air charge) and a CUT-OUT of 50 psi.

So when you turn on the pump you'll see pressure in the system go up to about 50 psi before the pump turns off.

Our Tank Pressure is Over 100 psi

At our water tank the gauge pressure is over 100 PSI and seems to stay there. What does that mean & what do I do? On 2017-06-14 by dave

by (mod) - pressure tank gauge not working + important urgent safety warning

It's possible that your gauge is jammed with debris and not registering the proper pressure.

Watch out: if your water tank pressure is really over 70 the system is unsafe: a burst tank could kill someone.

Immediately turn off the pump at the electrical panel and then bleed off pressure by opening a tap at a fixture nowhere near the tank.

I suggest making a separate water pressure measurement at a hose bib more laundry spigot.

We explain how to do that at WATER PRESSURE MEASUREMENT 

If you confirm that the actual water pressure in your system is safe - that is 70 psi or below for a typical residential water piping system, then read

• WATER PRESSURE GAUGE
• WATER PRESSURE GAUGE ACCURACY

Adjust the Air Pressure in a New Water Tank

What should be the air charge in an empty pressure tank?

The tank Will Fill When I Turn On the pump.

I want to know is should it have 30 psi in it now as it is empty. Only I tried filling it with air and it will not build any pressure in the empty Bladder Tank. (Jan 8, 2016) Thomas said:

Reply:

Thomas, when the pressure tank has no water in it at all its pressure can be set to 2 psi below the pump control switch CUT-IN pressure

So if your new pump control switch is a 30/50 switch (CUT-IN = 30 PSI, CUT-OUT = 50 psi) and if your new bladder type water pressure tank comes with an air pre-charge of 28 psi, you're all set. .

Do I have to adjust the factory pre-set air charge in the water pressure tank?

Just checking--looking to buy a new pump and pressure tank--most come now with factory presets.

If the pump presets are 30/50 and the tank preset is 18 PSI--do I have to adjust the pressure in the tank to 28 PSI? or cna I leave the presets as is. Is it better to buy a pump and tank that have the same presets? any info you can provide would be great! (Oct 15, 2015) Anonymous

Reply:

I would set the -re-set pressure to 2 psi below the actual pump control switch cut-in pressure. So if your new switch cuts in at 30 the pre-set pressure should be at 28.

I suppose that as-delivered the pre-set pressure was set to 18 psi so that the tank would work OK with a pressure control operating at 20/40 psi.

If you leave the lower factory pressure the draw-down water volume from the tank will be less than optimal for your higher operating pressure range.

 

Do I have to add water, then add air in to a bladder-type water pressure tank ?

Just installed a new bladder tank; doI have to drain it first, then add water, then then air back to it ?

Reply: No. Start with an empty tank. Set the correct air pre-charge, then allow water into the tank

Not if the factory precharge air pressure is correct for your system that is 2 psi below the pump cut in pressure.

When you are installing a new bladder type water pressure tank

1. Install the tank in position, connecting it to water lines, etc., but with water and pump turned OFF
2. Note the pump pressure control switch CUT-IN pressure.
3. Check the air pressure pre-charge in your tank and set it to 2 psi below the CUT-IN pressure on your pump control
4. Open the water valve feeding into the tank
5. Turn on the water pump