Troubleshooting a suction issue

[luna87]

So I've been fiddling with the pool all week trying to get it up and running properly.

I'm new to owning a pool as we just moved into this house in September and promptly had the pool closed. When I had the pool guy come out to open it he advised me that it was not closed professionally (different pool company closed it and is now out of business). The gizzmo was not installed properly, only 1 out of 4 jets had a freeze plug installed and based on the black color of the water probably didn't have proper chemicals added either. The pool guy couldn't get the pump to 100% prime, it will maintain about 80% water level but never fully prime. He recommended a full pressure test and quoted approx $1200.

So I started researching and trying a few different things, I think I have it narrowed down but am looking for more advice.

The pump seems to maintain a nearly 100% prime for an hour or so after startup. After that it slowly loses more prime until its down to about 80% where it remains stable. It seems that if it won't retain its "startup prime" unless the pump is off for a while and cools down.

Since I didn't see any heaved concrete or dirt or sand in the filter, I was pretty sure no pipes were broken as a result of the sub-par winterizing. My suction side to skimmer and main drain have old gate style valves, however, when starting the pump up and trying to achieve prime, running the hose over the valves seems to make no difference in achieving prime so I don't believe they are leaking.

I see no difference in prime when keeping only skimmer or only main drain, or both open.

To do my own version of a pressure test on the skimmer I bought a drain king tool and inserted it in the skimmer to pressurize the line between the skimmer and the pump, when I fully closed the valve to the skimmer the drain king eventually built enough force to blow out of the pipe (it came out like a shot!).

I noticed when turning the pump off, as the pressure equalized inside the pump it would spray water from the lid. I replaced the gasket on the lid and applied some pool goop, tightened it up and it no longer sprays.

So... for all of the reasons I listed above, I'm fairly certain that one of the other seals (impeller?) on the pump is actually the source of my suction leak... thoughts?

 

[Azgirl71]

I want to welcome you to TFP! I am sorry to say I don't have answer for you. There should be someone along shortly that will.

 

[JeffC]

I am a complete newb but I had the exact sample problem. Take what I have to say with a grain of salt.
I had a cracked pipe in the suction side near the pad. There was a small void that would fill with water. The suction of the pump would pull water from the void until it was empty then start to pull air but never loose 100% suction.

 

[pooldv]

I'm not a lot of help here either. But, I do have this link to a Pool School article that might help, http://www.troublefreepool.com/content/151-suction-side-air-leaks

And another might help.

 

[luna87]

any other thoughts on this?

 

[mas985]

So... for all of the reasons I listed above, I'm fairly certain that one of the other seals (impeller?) on the pump is actually the source of my suction leak... thoughts?

A seal is on the pressure side of the pump so it would leak water out, not air in.

The pump seems to maintain a nearly 100% prime for an hour or so after startup. After that it slowly loses more prime until its down to about 80% where it remains stable. It seems that if it won't retain its "startup prime" unless the pump is off for a while and cools down.

This is indicative of a broken underground suction side pipe. When the pump is off, water leaks out into the surrounding ground. When the pump is turned on, this water gets slowly sucked out until there is no more water in the ground and it starts sucking air which the pump then loses prime. Another forum member had this same issue not too long ago. Given that they did not close the pool properly and did not seal off the pipes, this may not be that far fetched.

But some more information might help narrow it down.

Has the filter pressure changed from it's normal clean pressure? Higher or lower?

After the pump has been off for some time, do you notice any areas from the pump to the pool where the ground is saturated with water?

 

[luna87]

A seal is on the pressure side of the pump so it would leak water out, not air in.

This is indicative of a broken underground suction side pipe. When the pump is off, water leaks out into the surrounding ground. When the pump is turned on, this water gets slowly sucked out until there is no more water in the ground and it starts sucking air which the pump then loses prime. Another forum member had this same issue not too long ago. Given that they did not close the pool properly and did not seal off the pipes, this may not be that far fetched.

But some more information might help narrow it down.

Has the filter pressure changed from it's normal clean pressure? Higher or lower?

After the pump has been off for some time, do you notice any areas from the pump to the pool where the ground is saturated with water?

Unfortunately I'm not sure if the filter pressure has changed since this is really my first season attempting to use the pool. My DE filter is around 30 psi when running

I don't notice any wet spots around the pool but i suppose it could be a small enough leak that i might not notice?

Sound like I might need to bust out the shovel...

 

[mas985]

30 psi is very high and could indicate a problem with your filter.

Does the pressure gauge read 0 when the pump is off?

Have you back washed the filter?

 

[luna87]

30 psi is very high and could indicate a problem with your filter.

Does the pressure gauge read 0 when the pump is off?

Have you back washed the filter?

the filter is very old and probably needs to be replaced. I plan to replace it once I can verify there isn't a very serious (and very expensive) plumbing issue. The gauge does read 0 when its off and it was backwashed.

I did just dig up some of the plumbing around the pump down to where it makes a 90 degree turn on the suction side (should have done it days ago). I seem to get a much more consistent prime when i run the hose over it but still not perfect so I'm guessing its leaking somewhere else too.

I can handle most plumbing tasks but am not that familiar with pool plumbing. Where the PVC makes a 90 degree turn it uses some kind of pvc adapter and stainless hose clamp to seal to what looks like black somewhat flexible plumbing. Is this standard practice for plumbing an in ground pool? seems very strange to me.

 

[mas985]

That sounds like black poly pipe and no it isn't used much anymore. It is subject to leaking.

 

[luna87]

lucky me! Just so I know where to look and what I'm looking for maybe you can help shed some light on how my plumbing may be laid out and how the black poly typically fails?

I'm guessing the black poly style plumbing primarily leaks at whatever fitting it uses to connect to another piece of poly or another style of pipe? It seems pretty rigid yet flexible, so I wouldn't expect it to leak for any other reason?

Is there a standard for how I can expect the plumbing to be run? as you can see in the picture there is alot of concrete all around the pool. The pool equipment is just off to the right in this picture (not shown) and the plumbing for the skimmer and main drain from what i've dug up so far seems to run parallel to the far side of the pool. As you can see there is alot of concrete around the skimmer, should I expect that much of that plumbing is inside the concrete pad or should that mostly be backfilled with something under the concrete? Sorry if that doesn't make any sense... just trying to get an idea of which way these pipes run before I dig up the yard.

 

[luna87]

So I spent some more time working on this today. I dug up all of the plumbing between the pump and the concrete pad where I really can't dig anymore.

I'm still getting a nearly complete prime that fades over several hours. After inspecting all of the plumbing I can see, I don't see any obvious places it is leaking.

On a suspicion that high filter pressure is causing an otherwise very small air leak to become a much bigger problem and the fact I had been planning to replace the filter anyway, I bypassed the filter and rigged up some plumbing to route directly back into the pool. So really I only have the pump pulling water from the main drain and skimmer. The pump now maintains an almost perfect prime with just a small amount of swirling bubbles all day and the flow rate coming out of my rigged up plumbing is more than I have ever seen.

With that being said - does it seem reasonable that I have a tiny suction leak somewhere that was made much worse by the fact that the pump is also competing with alot of back pressure from the filter?

I'm planning to replace all of the plumbing between the pump and the black poly including new PVC valves to replace the old gate style valves tomorrow once I've pumped the water level down low enough. I'm thinking replacing the potentially leaky joints and valves before the pump combined with a new filter will probably do the trick.

 

[mas985]

With that being said - does it seem reasonable that I have a tiny suction leak somewhere that was made much worse by the fact that the pump is also competing with alot of back pressure from the filter?

Probably not due to the filter pressure but it could be due to the suction side vacuum.

Bypassing the filter will usually increase flow rate on any plumbing system and with increased flow comes higher head loss and on the suction side, this manifests itself as higher suction which could pull a small leak closed. Also, with higher flow rates, it is easier to purge air out of the pump basket so you are less likely to notice any air. So either or both of these factors could be at work.

But given the filter pressure, I would say you do have a filter issue in addition to a suction side air leak.

 

[luna87]

In case an update can help anyone else out in the future... I re-plumbed the entire suction and return side of the system into a new Hayward Perflex DE filter last year (the old filter was completely shot and no parts available) using PVC ball valves instead of the old gate valves and the whole thing works like a charm. Those old gate style valves (or the plumbing around them) were in bad shape.