Water Pressure Measurement FAQs

Step by Step Guide to Checking Operating Water Pressure at a Building

Clarify the proper procedure to check operating water pressure

We have a Wellmate WM0075 unit. I was told this procedure to check operating pressure:

- connect hose & run water

- should drain pressure from 60psi (hi) to 40psi (lo)

- then should take ~25secs to build pressure back from 40psi to 60psi

However, I'm not clear on whether I'm to stop the water flow when it hits 40psi, or to keep the flow open, watching it climb back to 60psi.

With the flow off hitting 40psi, it takes ~22secs to get to 60psi, but with the flow open, it takes between 45-75 secs.

Can you please clarify? Thanks. On 2017-05-20 by Steve Pozgaj -

by (mod) - how To check "operating water pressure" at a building

When water is being used in building at a very fast flow rate or consumption rate, then it may be normal for the well pump pump to run continuously.

To check "operating water pressure" at a building you can make several measurements by simply connecting a pressure gauge to an outside faucet:

1. Measure the water pressure when the pump turns OFF and no water is being run in the building.
   
   This is the maximum pressure your building will see at that point. This is the pressure control switch CUT OFF pressure or CUT OUT pressure.
2. Measure the water pressure after water is run in the building until the pump turns ON.
   
   This is the pressure control switch CUT ON or CUT IN pressure.
3. Measure the water pressure when multiple faucets are being run
   
   in the building such that the pump is running continuously. This will approximate the maximum sustained water pressure when your building occupants are using water at a high rate. Naturally if still more fixtures are operating the building water pressure will be a bit lower.
4. Measure the water pressures as in cases 1 - 3 again at the highest floor
   
   in the building as this will normally be the lowest deliveed water pressure.

Water tank seems empty in seconds and pressure falls off quickly

I lost power to my pump after I switched the spot of the pump breaker with another breaker in my panel. I switched them back and had water. The next day I lost water pressure, water would come out in a trickle. I have a bladder in my pressure tank.

Since then I have fixed the wiring issue, cleaned and checked the power to the pump, replaced the pressure switch and still very little pressure.

If I do not turn the water on for a few minutes I have about 30 seconds of pressure before it fades. The pressure in the tank is set at 28psi for a 30-50 pressure switch. The tank seems empty. The pressure switch will click on and then click off after a very short time. Nothing seemed to fix the issue.

There is a water softener system in place with a filter after the softener. I noticed there was still water in the line to the filter. The filter is screwed into the line.

There is a handle on top of the filter that gives access to a red button that when I pressed I got air and then water coming out. Now I dont have any water. Can a collapsed bladder still have the 28psi? Could air be blocking water from getting to faucet? On 2017-12-07 by Rob

Answer by (mod) -

Rob,

Running out of water in the well can cause the symptom you describe.

If you leave water off for more than a few minutes and you see that you have more water (before running out) after that, the implication is that the flow rate of your well is poor and it needs a long recovery time.

The short click-on time suggests a water logged pressure tank.

The water pressure tank normally is about 1/2 to 2/3 full of water when the pump shuts off. Your tank pre-charge pressure is correct if you're measuring that under the right conditions: pump turned off, all water pressure drained from the system.

The button on the filter is to release pressure before unscrewing the filter base in order to change the cartridge.

I'd be sure you have pre-charged the tank correctly, then wait several hours or longer to see how the system behaves when you next run water.

Also check that water is actually entering the water tank. If when the pump turns off the water tank still seems empty (light) then the bladder may be stuck over the tank entry.

See WATER TANK BLADDER STUCK to ITSELF

 

Utilitech Water Tank troubleshooting & repair: gauge falls to zero

New Utilitech 20 Gallon Water Tank (Lowe's). Bringing up and "stress-testing" a completely new system. At one point I completely discharged all water from the tank, removed power from the pump, and opened faucets to release any remaining system pressure.

Then, to isolate the tank completely, I closed a shutoff valve between the tank tee and the system.

Here's the weird part. The pressure gauge at the tank tee naturally read zero upon draining it completely. HOWEVER, after a few minutes, the pressure begins to creep up and eventually equals the tank precharge pressure (currently at 38 PSI).

Is this a natural phenomenon (perhaps due to temperature change), or is there a pinhole leak in my new tank allowing precharge air to transfer across the diaphram to the "water side"?

The pressure at the top of the tank continues to read 38 PSI, but since the difference in volume on either side of the diaphragm is so great, I assume it would take a long time for pressure loss from a pinhole leak to be readable on a typical tire pressure gage. (Aug 17, 2016) Chris

Reply:

Chris:

An empty water tank that uses an internal bladder will have an air charge above the bladder equal to the tank pre-charge pressure (38 psi by your note). Perhaps air in the water-containing area of the tank is thus being pressurized by the pre-charge?

If there's a leak in the bladder I expect air discahrge to show up at faucets but perhaps the air leak is so slow that the air discharge isn't noticed.
But if the bladder leaks then ultimately I expect to see the pump start to short-cycle and I expect to see the draw-down water quantity reduced (before the pump turns on).

A second reason for a gauge to respond only slowly to pressure changes is debris-clogging of the gauge's sensor port; if you replaced the tank but are using an old gauge on the system that could be the case.

Watch the gauge when you pressurize and de-pressurize the tank. Does it sometimes stick or is it slow to respond?

Finaly re "closing the valve between the tank and the system" - I'm unclear on this. Is the tank isolated from the pump and controls but still connected to the house water supply piping?

I'd try to separately isolate the tank from 1. the pump side, 2. the house side, 3. both sides. That'd be diagnostic.

Chris said:
Thank you Dan.

"I'd try to separately isolate the tank from 1. the pump side, 2. the house side, 3. both sides. That'd be diagnostic."

I may have described the sytsem state unclearly, but yes, the tank is completely isolated from any and all plumbing systems. It is basically stand alone and capped off at the tee by a shutoff valve. In this state, the empty "water side" of the tank (as measured at the tank tee pressure gage)slowly creeps up in pressure until it equals the "air side" pressure. Currently set at 38 PSI. The entire system is weeks old, so no sediment here.

Unless there is a known phenomenon wherein the pressure on the water side of the tank would increase due to temperature changes, I can only otherwise attribute it to pressure bleeding across the diaphragm. UNLESS I am missing something that an experienced plumber would find obvious. :) And I am prone to missing the obvious!

Followup by Chris

Dan. Regarding the water-side tank pressure increasing, while isolated from all plumbing: It was indeed the temperature differential causing the pressure to creep up. As the well-water-chilled bottom of the tank climbed up towards ambient temperature, it was also increasing in pressure.

Once the whole tank was equalized at the same temperature, I released any remaining air pressure from the bottom and re-isolated the tank from all systems. At this point, the pressure at the tank tee remains at zero as it should, and no longer creeps up towards pre-charge pressure.

It was the temperature difference.

Case closed. In case you ever get a similar question, you can now say, "yeah, that's a thing." :)

Reply by (mod)

In detail at WATER TANK BLADDER CONSTRUCTION we discuss the cutaway of one version of a bladder-type pressure tank that you'll see in the photo I include here:

you'll see a small VENT hole in a metal dome that separates the water-holding area of the tank (in the tank bottom) from the air reservoir area of the tank (in the tank top).

When you empty the tank of water the bladder collapses downwards and the water pressure falls to zero or near-zero; there may be a tiny bit of water left in the system or if the water side was drained air could have entered the water side of the pressure tank.

Here's an image inspectapedia.com/water/Water_Tank_Bladder_416_DJFs.jpg

When you totally isolate the water tank, the air at the pre-charge pressure passes through that vent opening and slowly pressurizes the bottom or water area of the tank. That might be pushing enough on the bladder that if there is air or water remaining in the isolated bladder space you'd see the water-side pressure go up to the pre-charge pressure.

That sounds OK to me.

When the tank is re-pressurized using this approach, and you see pressure on the water side, open the Tank Tee valve and see if some water or air comes out; a small shot should emerge, then nothing further. If air keeps coming out then yeah the bladder has a leak.

 

Do I need to verify the factory-set air pressure in my water pressure tank - will that fix bad house water pressure?

I have a Well-X Trol (size to be verified tonight)pressure tank.
If water is being utilized at one fixture, pressure seems to be non-existant at any others.

My pump cuts-in/out at 30# & 50# on the nose, with no aparent short cycling.

After reading this (incredibly informative) WATER TANK BLADDER PRESSURE ADJUSTMENT page, can anyone verify my assumption that I need to verify my factory set pressure? (disable pump, drain, check pressure, add if needed) - Scott J 1/9/2012

Reply: no, no.

Scott J,

We need to distinguish between water pressure and flow rate or quantity.

Static water pressure when no water is running shows us the system maximum water pressure possible after the pump has cut off at the "cut out" pressure set by the pressure control switch.

Active water "pressure" and flow rate: if you have normal water pressure in the system at one fixture but inadequate or very little pressure as soon as a second fixture is turned on, that suggests that there is a water delivery problem - often traced to clogged piping or a control valve that is partly closed somewhere.

The pressure in your water pressure tank determines the length of the draw down cycle - how long water can run before the pump has to turn on. It is the pressure control switch and pump and well capacity that determine the system functioning water pressure and flow rate.

So from your complaint, I may be mistaken but I don't quite see how changing the pre-charge pressure in your water tank would help. I'd leave it alone. Instead, see

WATER FLOW RATE CALCULATE or MEASURE  - for how to measure what your system is doing
and see

WATER PRESSURE LOSS DIAGNOSIS & REPAIR - home

to further diagnose the trouble.