Pressure question

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A

adrian300

Well-known member
Sep 27, 2021
52
California
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi there. We have an old pool, 25k gallons, with old 1 1/2” pipes. However, the previous owners installed a pentair VSP with 2” pipes, and solar water heater. The pipe reduction from 1 1/2” to 2” is causing cavitation and the pump to lose prime at high speeds. We’ve gotten some quotes on repairs. Some contractors are saying a full replumb would be necessary, others are saying just run it with the air bubble since it’s still pumping water and not running dry.

One contractor is suggesting we install a new skimmer, and replumb the suction side with 2” pipes. This sounds like a good plan, but my worry is that we still have the 1 1/2” pipes on the return (once water returns from the solar heaters). Will that cause a pressure differential issue, or is that a viable fix?
 
adrian300 said:
The pipe reduction from 1 1/2” to 2” is causing cavitation and the pump to lose prime at high speeds.
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That should not cause cavitation. What makes you think that is the cause? Cavitation is NOT air in the pump basket. That is an air leak.

Cavitation can only be detected by the sound. It sounds like gravel is going through the pump.

It sounds more like an air leak to me. Check the pump lid gasket and drain plug gaskets and lube both with pool lube.
 
mas985 said:
That should not cause cavitation. What makes you think that is the cause? Cavitation is NOT air in the pump basket. That is an air leak.

Cavitation can only be detected by the sound. It sounds like gravel is going through the pump.

It sounds more like an air leak to me. Check the pump lid gasket and drain plug gaskets and lube both with pool lube.
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Appreciate the reply. Cavitation might be the wrong word. We had a leak detection company come out and pressure test, and they did not find any suction side leaks. I've replaced the pump lid, o-ring, etc with no luck. We have a variable speed pump, and at lower RPM's there is no to little air, but at higher RPM's there is a large bubble.
 
Adrian,

You need to find some better and trustworthy contractors.. You are being taken for a wild ride.

I have two rent house pools that have mixture of 1.5" and 2.0" plumbing, they also have 3 HP IntelliFlo pumps. They both work just fine...

From a plumbing size point of view, you just do not have a problem.

Please tell us what does not work?? What actual problem are you trying to solve?

What speed does the pump normally run? What speed are you running where there is a bubble?

Thanks,

Jim R.
 
Unless the bubble is more than the size of a baseball, I would not be concerned. If the water level in the pump basket drops below the inlet pipe, then you have a problem.
 
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I mean, yeah, it's working. But when the booster pump is on for the sweep, or I am increasing RPM to 2500+ to pump up to the solar water heater, the air bubble is a good 6 inches and the pump runs a bit dry. The pump has lasted just fine for 3 years or so, but my worry I guess is having to replace the pump because it burns out.

If it's not a plumbing issue that's great news, but it puts me back to finding the culprit of the air leak, which the leak detection company couldn't identify.
 
adrian300 said:
I mean, yeah, it's working. But when the booster pump is on for the sweep, or I am increasing RPM to 2500+ to pump up to the solar water heater, the air bubble is a good 6 inches and the pump runs a bit dry.
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6" in width or depth. Again, unless the level drops below the inlet pipe, the pump is NOT running dry. Do you see air coming out of the returns during this time? What about at full speed? Does the bubble get bigger?

adrian300 said:
The pump has lasted just fine for 3 years or so, but my worry I guess is having to replace the pump because it burns out.

If it's not a plumbing issue that's great news, but it puts me back to finding the culprit of the air leak, which the leak detection company couldn't identify.
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Air leaks are often difficult to find. Air leak companies use pressure which can hide a suction side leak as leaks are not always symmetrical.

If you have already replaced the pump lid gasket and drain plug gaskets, then I would look to any suction side valves. Can you post a picture of your pad equipment?
 
I only have the issue when running the solar, or the booster pump. At low RPM's the air bubble is small.

At high RPM's, the bubble is around 6 inches deep. When the solar heater and the booster pump are running, the pump is nearly dry. I see air coming out of the returns all times that the pump is running, but small champagne bubbles at low RPM and big quarter sized bubbles at high RPM.

Maybe not easy to see from the pictures below, but there aren't any valves on the suction side. I thought there was a skimmer leak, but pressure testing

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What about when solar valve is off and the pump is at full speed? Are there still bubbles?

You may have two issues. The solar VRV may be sucking in air because the RPM is too low. But you may also have an air leak on the suction side.

I believe that pump has a threaded inlet. One thing to try is to put a heavy coat of pool lube at the junction where the threaded pipe meets the pump housing. Right in that corner along the threads. If it is leaking there, it will suck in the pool lube and seal the leak at least temporarily.
 
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Yeah still have air passing through when solar is disabled, and the bubbles get larger at higher RPM's. I also tried shaving cream and pool lubricant on all of the PVC joints on the suction side but didn't seen any leaks.

I guess another question I have, is if I just keep running it as is, what are the risks? That the pump will burn out sooner than normal and I will need to replace it?
 
adrian300 said:
Yeah still have air passing through when solar is disabled, and the bubbles get larger at higher RPM's. I also tried shaving cream and pool lubricant on all of the PVC joints on the suction side but didn't seen any leaks.
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Sounds like a suction leak and not a solar issue. Another possibility is that it is sucking in air from the skimmer. When at higher RPM, look at the skimmer and see if a vortex is forming which can suck in air.

adrian300 said:
I guess another question I have, is if I just keep running it as is, what are the risks? That the pump will burn out sooner than normal and I will need to replace it?
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Only if it actually stops pumping water. As long as there is water moving through the pump, there is no real issue except the bubble out of the returns.
 
mas985 said:
Sounds like a suction leak and not a solar issue. Another possibility is that it is sucking in air from the skimmer. When at higher RPM, look at the skimmer and see if a vortex is forming which can suck in air.


Only if it actually stops pumping water. As long as there is water moving through the pump, there is no real issue except the bubble out of the returns.
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So I don't see a vortex on the skimmer, and the leak detection company didn't find a leak with the skimmer, but speaking with others in the area they mentioned that we have a "black bottom" skimmer which is a type prone to leaks.
 
Looks like it is a thing:

Suction Side Leak -- Black Bottom Skimmer?

Hi all, I believe I have a suction side leak, I am getting air in the pump and have tried most methods of diagnosis, unsuccessfully. A contractor I reached out to mentioned that I have a "black bottom" skimmer, which is prone to leaking. Does anyone have familiarity on whether this is true...
www.troublefreepool.com www.troublefreepool.com
 
mas985 said:
Looks like it is a thing:

Suction Side Leak -- Black Bottom Skimmer?

Hi all, I believe I have a suction side leak, I am getting air in the pump and have tried most methods of diagnosis, unsuccessfully. A contractor I reached out to mentioned that I have a "black bottom" skimmer, which is prone to leaking. Does anyone have familiarity on whether this is true...
www.troublefreepool.com www.troublefreepool.com
Click to expand...
Ah yeah that was me too hehe. It's been an issue for a while.
 
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