Mystery: Zero pressure, but everything else seems fine

dabramet

0
Bronze Supporter
Dec 31, 2018
21
Walnut Creek
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
Hello all. I've been struggling with this issue of zero pressure for 5 years. Here's the facts:
1. filter pressure gauge reads zero at all times. A few years it ago it might have got to a few PSI, but now its always zero.
2. I've replaced the pressure gauge at least 3 times. No impact.
3. i've replace the pressure valve. No change. the pressure release valve works fine, meaning it bleeds the excess air and then water comes shooting out.
4. outlet water pressure seems fine. It's never been a gusher, but its strong enough to the touch on the outlets.
5. no apparent air leaks on suction side found. I've replaced o-rings everywhere, tested with soapy suds, replaced filter basket lid, made sure water level is always good, keep the skimmer basket clean.
6. I've checked the impeller for debris (there was essentially none).
7. I've cleaned the filter cartridge regularly, i test water chemistry regularly.
8. the pool is probably at least 25 yrs old.

Yet, I can't understand why the pressure gauge is always zero. When I first took possession of this pool 6 years ago, the pressure was high, say around 45 psi. I cleaned the filter and pressure dropped to 2 psi. Later, as pressure rose to around 10 psi, I cleaned the cartridge again. After that, pressure has been zero. Yet the fllter seems to work well, the water stays clean, I don't seem to have a water leakage of meaningful size.

My equipment facts. I have an old Sta-Rite Posi-Flo stainless steel 135sqft "silver bullet" filter system, connected to a Max-e-Glas II pump with a 1.65 HP motor. I've ordered a variable speed upgrade kit for this system, I'm hoping maybe the process of replacing some old parts in the pump might help with the mysterious pressure issue.
 
I replaced the gauge today with a new one and when I removed the old gauge, I looked into the pressure valve and it looked clear. I could hear and feel air sucking into the valve through the opening where the gauge goes. Also like I said the pressure release valve works fine, so water and air is getting through the filter housing hole at the top, to the pressure valve.
 
Are the filter inlet and outlet reversed?

What is the filter model number?

Can you show the filter label?

Can you remove the cartridge and show what it looks like before you clean it?

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I replaced the gauge today with a new one and when I removed the old gauge, I looked into the pressure valve and it looked clear. I could hear and feel air sucking into the valve through the opening where the gauge goes. Also like I said the pressure release valve works fine, so water and air is getting through the filter housing hole at the top, to the pressure valve.
Remove the air-relief assembly entirely from the nipple that is built-in to the tank and be sure that port is completely clean. They sometimes get enough debris in them that won't allow water-pressure to reach the gauge. Do the same with the plastic air-relief assembly. If you have a really old one, the whole assembly will be a brass part.
 
You need some way to block the top hole or the water will not go through the cartridge.

You need a center core or the top needs a center tube or the cartridge needs to be closed at the top somehow.

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That's an American Pool Products Predator, now Pentair Clean and Clear, not a Sta-Rite Posi Flo, as in all your pictures. It uses a conventional-design cartridge and uses that removable core as the seal at the top.
Posi Flo uses this cartridge and the top (blue) is sealed, bottom (orange) is open to return the water.
1725897436539.png
 
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Maybe they have the wrong cartridge?

Maybe the Inlet and Outlet are Reversed?

Is the flow good from the returns?
Wrong cartridge? Nothing else will fit, though a smaller one of the same filter, 100, 70, 50, 25 will. There would still be pressure in the tank.
Inlet/outlet reversed? If the cartridge didn't lift off the base, it would be very expanded, water would flow out the inlet port and there would be pressure in the tank.
If the air-relief manifold isn't clogged, it is probably the nipple that is built into the tank that usually is as long as all else if working.
If the filter is old enough, there used to be a very small brass screen at the top of that nipple that also clogged easily. It could be in the manifold as well. Really having to go back in the memory vault for that bit of trivia.
 
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Definitely odd.

Maybe put a pressure gauge at one of these locations to see what reading you get.

Be careful when installing into plastic threads because the plastic can crack if brass threads are screwed in too tight.

1725898770671.png
 
The only other odd this is that my filter seems to run clean at only 2-3 PSI.

When I first got the home, the gauge was old and broken. I replaced it and pressure went to 20 psi.

After a thorough cleaning of the cartridge it went down to 2 psi.

The gauge is new, I just installed it last weekend. It sits at zero when the system is off and jumps to 2-3 psi once turned on.

Filter pressure increased slightly to about 5 psi.
 
Update: I installed a new motor and upgrade kit, this one Sta-Rite Dura-Glas II Pump VS Motor Upgrade Kit - 1.65HP - INYOPools.com

While taking out the old motor, I found the difuser completely cracked in two pieces. I think this was the main problem, because once I finished the install with all the new upgrade kit parts and started it up, everything was working better! Pressure gauge showed 9 psi, the return jet in the pool was much stronger, and the motor is much quieter. I wish I had done this 5 years ago. Thanks all for your help!
 
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