Pool pressure gauge

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Pool pressure gauge

Postby randy » Tue 09 May, 2006 16:41

I have an undergrood pool which is 15 x 35 and the pressure on the gauge reads always around 30 psi. My guage is new and is drops down to 0 when it's off , so that's not the problem. I was wondering if 30 psi is normal or does it have to be 18-20 psi. My filter tank cracked. Could it be because the pressure is to high?
randy
 

Postby Pool User » Sun 24 Dec, 2006 16:04

what is the right water pressure, anyhow?

i've got a 20 x 40 inground pool, and pressure is at 20 psi all the time, is this right?
Pool User
 

Postby Pool User » Sun 24 Dec, 2006 16:49

Anonymous wrote:what is the right water pressure, anyhow?

i've got a 20 x 40 inground pool, and pressure is at 20 psi all the time, is this right?


anyone?
Pool User
 

Postby dynamictiger » Sun 24 Dec, 2006 17:32

The pressure gauge usually installed on a domestic pool is installed on the inlet side of the filter.

This gauge measures all the pressure in the system from the return jets, including all the pipe and fittings underground and then filter pressure drop as well.

It is not possible or practical to determine if a pressure is too high or too low without engineering the system. However simple logic tells you that if you increase the pump size and try and pump more water the pressure goes up and the reverse is also true.

Most domestic pool pumps curves top out around 25 metres or 36.25 PSI, whilst it may be possible to get higher heads this is pretty average. Of course this depends on pump size and manfacturers tolerances.

Most domestic pool filters are designed to handle a pressure of about 30 metres or 43 PSI on a continuous basis, although this varies from manufacturer to manufacturer.

The usual culprits for cracking a filter or similar damage are:
-Age
-Air
-Water Hammer

The first is obvious. The other two are related in simple terms air can become trapped in the system somewhere not necessarily in the filter, although this is common. A phenomenon occurs where the pressurised water increases the pressure on the air until the air reverse flows against the current. This is termed water hammer. Water hammer can be seven times the pressure applied. So for example at 30 PSI the hammer pressure could be as high as 210 PSI. Fortunately this is very rare as most pool builders and pipe work installers understand this and build it out of the system. This usually only occurs if the pool has been drained and refilled as the water hammer in a pool system usually only happens once.

HTH
dynamictiger
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Postby Pool User » Wed 27 Dec, 2006 16:58

Dynamictiger, has provided some good information. There is no “right” pressure for all pools; however, all things being equal, the lower the pressure in the filter the more efficient the flow (15 psi to 20 psi or 35- to 45-foot pressure head) is usually relatively efficient if you look at most swimming pool pump curves (assume 5- to 10-foot suction head). Therefore, you may want to consider changing to a smaller pump motor next time it needs changing (or of you want to save electrical cost now). There are a few good websites available that discuss the advantages of reducing the pump motor horsepower (HP) for more efficient pool water circulation (I will provide links in my blog noted below shortly).

More important…You said that your filter is cracked. This could have significant safety concerns because of the potential (pressure) energy (force). At 30 psi a 24-inch diameter filter has a force of over 13,000 pounds (two Hummers) [Force = Pressure x Area … 30 psi x pi (3.14) x 12 inches x 12 inches = 13,000+ pounds]. You should probably replace the broken part or replace the filter (increasing the filter size/flow may also reduce your system pressure and increase the efficiency).
Pool User
 

Postby jednav » Thu 28 Dec, 2006 14:08

good write up, gentlemen!! just wondering?

my pool, inground, 20 x 40 ft, hayward superpump 1.5 hp with sandfilter, multiport valve.

water pressure is constant at 19-20 psi, but when i switch lever to recircular (sp) meaning bypassing filter, water pressure drops to 15 psi.

query: is this normal?

thanks
inground 20 x 40
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Postby dynamictiger » Thu 28 Dec, 2006 15:13

For calculation purposes we normally use 20 kPa for a clean sand filters pressure drop. This is about 3 PSI. However this is just the sand, you also need to take account of your MPV and unfortunately some of these have very high PD indeed, and your lateral system. I would think that the difference of just over 6 PSI is fine and nothing to be concerned about at all.

HTH
dynamictiger
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Postby Pool User » Sat 30 Dec, 2006 17:07

dynamictiger wrote:For calculation purposes we normally use 20 kPa for a clean sand filters pressure drop. This is about 3 PSI. However this is just the sand, you also need to take account of your MPV and unfortunately some of these have very high PD indeed, and your lateral system. I would think that the difference of just over 6 PSI is fine and nothing to be concerned about at all.

HTH


Thanks for the reply. Happy New Year!!
Pool User
 

Postby jednav » Tue 09 Jan, 2007 14:29

dynamictiger wrote:For calculation purposes we normally use 20 kPa for a clean sand filters pressure drop. This is about 3 PSI. However this is just the sand, you also need to take account of your MPV and unfortunately some of these have very high PD indeed, and your lateral system. I would think that the difference of just over 6 PSI is fine and nothing to be concerned about at all.

HTH


thanks for the info!!
Cheers
inground 20 x 40
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Sand Filter Pressure VERY low

Postby christy » Mon 02 Jul, 2007 19:50

Hi everyone,
I am new to owning a pool. We bought a house and it was here. Everything had been going pretty good since we got it clean and running. A few weeks ago after backwashing the pressure was at 10psi. It has remained at 10psi for about 3 weeks. I made the bad choice of backwashing because I had been vaccuming and thought I should. Well now the PSI is at like 2. I know this can not be good. What do I do? What happened? How do I get it back up to 12-15 PSI. The motor sounds fine, but there is weak water pressure coming from the return.
The gauge is brand new too.
Please help!
christy
 

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