Very low filter pressure

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PSmith307

0
Dec 20, 2016
8
Panama City, FL
My brand new sand filter has a 0-60 psi gauge on it, but never reads above 3 psi. After backwashing, and 99 % of the time, the gauge reads 1 psi. Everything about my pool is under warranty, so I called the PB out and they seem to be baffled. Today they added more sand, although they said it was 3/4 full and that is normal. Still reading 1 psi after adding sand.

I am thinking maybe the valve is malfunctioning. Any other ideas or help would be greatly appreciated. I am concerned that it is not operating correctly, although the pool water is crystal clear. But maybe this low pressure is normal for some small pools?

EDIT - The gauge has been replaced 3 times. All read the same.

Thanks in advance.
 
First question is how is the flow? If your flow is good, which I assume since you are crystal clear, then maybe a faulty gauge (oops just saw your edit!). Most folks use a 0-30 psi gauge since pressure is rarely over 20 psi for increased accuracy. Do you have eyes installed on your returns? There was one user here who's installer failed to install the adjustable eyes on the returns whenever they installed an automatic cover. I am not for sure why they didn't use them, but their pool also showed low pressure.

Last question, if you turn the pump on with the gauge removed do you get a lot of water coming out of the connection? Maybe there is an internal blockage like thread dope/tape in the fitting.
 
P,

Even though I hate to do it, I have to agree with that "Green Bay, Packers" lover, Pool Tool... :poke: The first thing to check is how much water pressure do you feel coming out the pool return eyeballs? How many eyeballs and what size openings?

I would think, with a single speed pump you should have a much higher filter pressure.

How about showing us a picture of your equipment pad.

Thanks for posting,

Jim R. (Still trying to recover from Sunday's broken heart!!!)
 
The pressure on the top of your filter is affected by a lot of factors all of which go into determining the total dynamic head of your plumbing systems and general pool layout. It also depends on the size of your pump (horsepower) and filter throughput (how much head loss the filter has). If you are getting strong flow at your returns, then low pressure could be normal.

As a suggestion for the future, many of us here use the glycerin-filled pressure gauges that read 0-30psi in 0.5psi increments. They are very accurate, well made with heavy-duty metal hosings and glass bezels and typically last a lot longer than the standard OEM gauges that the manufacturers put on their filter. Since your filter may be normally reading low pressure, having a more finely calibrated pressure gauge can be very helpful in seeing pressure rise over time.
 
Some things to check.

If the filter gauge is higher than the pool, it will lose 1 psi for every 2.31 feet it is above the pool surface. How high is the gauge above the water surface?

Some gauges don't start at zero. They can start at 3 to 5 psi.

The multiport might be plumbed incorrectly. The line from the pump should go into the highest port of the multiport.

There could be a suction side blockage. If any doubt, you could get a vacuum gauge and check the suction pressure.

What exact pump and filter do you have?

What is your plumbing size and distance from the pool?
 
P,

I would have thought the "thing" on your sundeck, which I assume is a bubbler, would be very active, but I don't see that in your pics...

It appears, but hard to tell in the pics, that you have a lot of bubbles under the see-through lid on the pump?? Is your pump full of water or is it half air?

As Matt says, it may be normal, but better to make sure.

Jim R.
 

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Just-a-PB said:
That is interesting James,
Have not heard that one before.
Can you explain the science behind that?
Click to expand...
Basically, just the weight of water. A 1 square inch column of water 2.31 feet high weighs 1 lb. The water in the filter will flow (fall) back to the pool under its own weight.

When the pump is off, the water will flow (fall) back to the pool if the system is not air tight. If it is air tight, there will be a vacuum in the filter that keeps the water from going out of the filter.

A filter gauge that can show vacuum would show -2 psi with the pump off if the gauge is 4.62 feet above the pool.

The vacuum is evident when the air relief is opened and air gets sucked in.

If a vacuum pump were put on a pipe where one end was in water and the other end extended up, it would take 10 psi of vacuum to get the water to go up 23.1 feet.

The limit that the vacuum pump could lift the water would be less than 33 ft because the water would begin to boil and less than 34 due to atmospheric pressure.*

A similar thing happens in diving where the pressure increases as you go deeper. For every 2.31 feet you go down, the pressure increases 1 psi.

*Note: Vacuum doesn't really lift water, it removes pressure so that atmospheric pressure pressure can push it up. Normal atmospheric pressure at sea level is about 14.7 psi. 14.7 x 2.31 = 34 feet.
 
A little Devils' advocate here------not that one psi is gonna matter much to anyone. BUT...if the filter is always full of water and the gauge sits right on the filter, I don't see where the 2.32678942 feet difference comes into play.
 
Water pressure drops with an increase in elevation or height within the water. Same reason there is crushing pressure at the bottom of the ocean. So if the gauge is about 3' higher than the pump, the pressure will read a little over 1 PSI lower than if you had the gauge on the pump drain plug. The weight of the water causes the pressure difference.
 
For that filter, 1 psi is low. Typically, the normal pressure is 8 to 12 psi depending on the pump.

It might be a problem or the pressure might be higher than it seems. Most systems are at ground level, if yours is significantly higher, that would make a difference.

When reading the gauge, count backwards from 10. Sometimes the first mark is higher than 0.
 
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