Suction side leak?

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Dave_NJ

Dave_NJ

Silver Supporter
Aug 15, 2019
109
North NJ
Pool Size
24000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
I just replaced my existing Hayward 1.5hp pump with a new CircuPool 3hp pump, added a swcg and redid all of the piping from the suction lines coming out of the pad to the jandy valves for the return jets. I have two very slight leaks I need to address but they are very slow drips, maybe once every 10 seconds.

What has me concerned is I now have an air bubble in the pump basket. After initial startup the lid is clear but over time a bubble develops and keeps getting larger the longer the pump is running. It's bad enough that after an hour or so the water level inside the pump basket drops about an inch and I'm concerned leaving the pump running overnight and burning out if the water level gets too low. The problem exists regardless of pump speed

Any ideas on how I can start troubleshooting this? I greased up the o- ring for the lid but that didn't do much. I just can't believe with no real leaks the water level can drop so fast.

When I drained my system before doing the work I stupidly left the suction and return valves opened so a good amount of DE backwashed into my pool. I'm cleaning it out and added a sock to my skimmer, is it possible the DE is clogging up the sock and not allowing enough water back to the pump??

Any help is greatly appreciated!
 
So quick follow up, at higher speeds (2500rpm) the air bubble is still there but doesn't increase in size, however I then get air bubbles coming out of one of the return jets which doesn't happen at lower speeds
 
Hard to say for sure as it's normal for a VS to develop a lid bubble. It's usually smaller with higher speeds. I notice most VS pumps stay full at more than 2000 rpms. With a swg you will get bubbles and burps coming out of the system randomly as it's making chlorine. When the pump primes it should be full and no air afterwards. If it doesnt you have air getting in. Where in the system do you have the drips?
 
Dave,

Did you use pump unions to connect your pipes to the threaded input and output connections on the pump?

Try using a garden hose and slowly run water over your input pipes, valves, etc. while watching the air bubble.. I'd run at about 3K and see if you can make the bubbles come and go using the water.. Basically the water closes the air leak.

Show us a pic of your pump install.. and tell us where the "slow drips" are...

Thanks,

Jim R.
 
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Here are some photos, sorry i can't get wider shots it's pretty close quarters.

Some info on my system:
  • suction and return lines are all 1.5";
  • I have threaded unions on both ends of the pump (I pretty much have unions everywhere...);
  • running at 1500 rpm filter pressure reads 3 psi, at 2500 rpm pressure is 11 psi (for comparison my system with the old pump would run at 18-19 with fresh DE);
I went ahead and replaced the skimmer sock which was pretty filthy, also backwashed, drained and recharged my filter. I fixed the slow leaks and disassembled every union and lubed the gaskets with silicone.

This is my first VS pump so if bubbles in the basket lid are typical that's good news. The bubbles coming out of the return jet were not from the SWCG, it was more like water hammering. A very short burst of bubbles were coming out intermittently and were fast enough that I could hear it from the opposite end of the pool. It was almost like the pump was forcing some of the air that was trapped out through the lines.

Anyways I appreciate the quick replies, will try the water test later today.

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I realized I never answered where the leaks were: one was the threaded part of the union on the pump discharge, other leak was the union connection between the MPV and the jandy bypass for the heater.

@sktn77a I used enough lubricant to coat the gasket with a thin film, is that enough or should I add more lubricant?
 
I did a bit of experimenting, at lower rpms (1500) the water level in the pump basket will slowly drop. If I turn it up to 2500 rpm the basket will fill most of the way up except for a small (2"-3") bubble under the lid. I let it run again at 1500 and the cycle repeats itself.

Is it possible for a pump to discharge more than it's taking in? I'm going to see the lowest speed I can set without having the water level drop
 
Dave,

Some other things to experiment with..

Try running with just the skimmer
Try running with just the main drain
Try running with the heater by-passed

As a general rule, you can't run much less than 1500 to 1800 RPM when you have a heater and a SWCG..

At low RPMs bubbles under the pump lid are normal.. What is not normal is for the bubbles to get larger and larger and for the water level in the pump to drop.. That normally indicates a suction side air leak. The longer it takes for the bubbles to increase, the smaller the air leak.

The three most likely things to cause a suction side air leak are... The O-Ring under the pump lid, the threaded connection at the pump input, and the O-Rings in the Intake valve.

Thanks,

Jim R.
 
So I did some more testing today, here are the results:

Tried running water over the suction side union and where the union threads into the pump but couldn't see any noticeable change in the bubble. I'm going to try again later and see what the results are because it was about a million degrees and I wasn't sure if the hose or the sweat dripping off my face was contributing more water...

If I turn the pump up to 3k rpms the bubble disappears in around 5 minutes and the lid is perfectly clear. If I reduce the speed to 1800 rpms I can see very small bubbles coming in from the suction side. After a half hour or so I will have a small (1/4"-1/2") bubble in the lid. I will check back later tonight and see how big the bubble is after running for 5-6 hours.

I lubed the heck out of the pump lid o-ring just to be sure.

If I shut off the pump no water drains out of the system so it looks like it's maintaining a vacuum.

Besides being an annoyance is there any real problem with an air leak? Obviously I don't want the pump to run dry but if I have to program the pump to run at 3k rpms for 5 minutes a day that's not the end of the world. My intent is to run the pump 20 hours a day at 2800 rpms and 4 hours a day at 2500 rpms. I may wind up changing that to just run 24/7 at 1800 rpms depending on how the skimming action is.
 

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Quick update: I've been fiddling around with rpms, timing, valve positions, etc. It seems everything has reached a state of equilibrium, the bubble under the lid never goes away but it has also stopped getting larger even at slower rpms. My current schedule is 1500 rpms for 21 hrs 50 minutes, 2500 rpms for 2 hours (skim pool surface in the morning) and 3000 rpms for 10 minutes to purge any air in the lid.

As time goes on I will probably eliminate the 3000 rpms cycle but for now I will leave it.

On another note is there a minimum pressure I should be looking for? I originally set the speed for 1400 rpm but the pressure was just barely registering on the gauge so I bumped it up to 1500 rpm which gives me 1.5 psi. I know lower pressure is generally better but is there such a thing as too low?

I bought one of those fancy glycerin gauges from TFT so I can more accurately track pressure but it hasn't arrived yet :(
 
Eh not really, I'm just home a lot these days (thanks Covid!) and it's nice to see a clean pool surface.

I have a few trees around the pool and the pollen has been nuts so I do get debris but in all honesty I could get away with running the pump only when the SWCG is on (4 hours) and maybe another hour or so in morning.
 
Get skimmer socks and run the pump 3hrs in morning in higher speed amd again in late afternoon. Pumps have a lifespan it's like mileage on a car. Plus electricity, the plus to a VS is to run slow to just have enough flow to satisfy the swg. Otherwise full power romps to skim well for cleanups once or twice a day
 
I decided to try and definitely check if I had a suction side leak. I bought this adapter:

Dura Schedule 40 PVC MHT x MPT Adapter - MHT Size : 3/4" - MPT Size : 1-1/2" (Part 503-015) - - Amazon.com

Dura Schedule 40 PVC MHT x MPT Adapter - MHT Size : 3/4" - MPT Size : 1-1/2" (Part 503-015) - - Amazon.com
www.amazon.com

and threaded it into the bottom of my skimmer. I set the suction valve to close off the floor drain and closed the return jets. I hooked up a garden hose to the adapter and turned it on with the idea being any suction leak would also leak water when pressurized.

First attempt I just opened the hose wide open and the pump lid basically blew off (oops).

Second attempt I opened the hose slightly and watched the pressure slowly rise from 0 until the lid blew off around 40 psi.

Third attempt I slowly opened the hose and shut it off when the filter gauge hit 25 psi. Everything was dry with no leaks.

With everything shut off the pump basket remained full, no water drained back down.

It looks like everything is fairly well sealed, I've been told that a VS pump will generate air bubbles just curious why that is.

Jimmy I've been slowly changing my run schedule so the pump runs less and less, right now I'm at about 12 hours a day.
 
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jimmythegreek said:
Hard to say for sure as it's normal for a VS to develop a lid bubble. It's usually smaller with higher speeds. I notice most VS pumps stay full at more than 2000 rpms. With a swg you will get bubbles and burps coming out of the system randomly as it's making chlorine. When the pump primes it should be full and no air afterwards. If it doesnt you have air getting in. Where in the system do you have the drips?
Click to expand...
Any thoughts on why a VS has a lid bubble and why the size varies with RPMs. I get a bigger bubble at 2250RPM then 2500 and am trying to make sure it isn’t a suction side leak.
 
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