Blockage on Suction Side? (I hate plumbing!)

[MasterTinkerer]

Moved into a new house with a pool in July of last year. Thus far, I have been very disappointed in the half-assed work done by the previous owner... but there is too much material for just one thread

Current issue:
I filled the pool over the weekend {https://www.troublefreepool.com/threads/131593-A-Whole-Series-of-Problems-(and-a-bunch-of-questions} and fired up the pump. The good news is that the leak is fixed... the bad news is that it is not pulling enough water through the skimmer inlet.

If I shut down the butterfly valve for the skimmer intake, the water continues to flow but the pressure drops (as expected) because it is still pulling water through the drain at the bottom of the pool.

However, if I shut down the butterfly valve for the drain, and leave the valve open for the skimmer, I lose suction. It will pull some water, but not much.

I have also noticed that sometimes it is pulling more water through the skimmer than other times. This can be observed both by the pressure at the pump and by the physical movement of water at the skimmer.



What I've tried:
I took out the drain plug out of the pump strainer and hooked up my air compressor. I thought I could blow out any debris that could be stuck in the line. It blew a bunch of bubbles in the strainer and spit out a few leaves, but nothing that would be large enough to suggest an intermittent blockage.

I've also made my garden hose fit tight into the hole in the skimmer box and flushed water through the line. Water pours out into the pump strainer, but no signs of anything flushing out.



What I think I'll try next:
Drain the pool back under the skimmer again and repeat the air compressor exercise to empty the line of water... then hook up the shop vac at the skimmer box and see if I can suck out anything.

If that doesn't yield any results, I guess I'm going to have to tear out all of the above ground plumbing at the pump.



My question:
Before I spend too much more time and energy in another exercise in futility - are there any suggestions? Anything else I should check or do?

My theory is that there is something stuck in the line that is just big enough to not pass through some point in the plumbing (checkvalve maybe).



Thanks for any recommendations or advice.

 

[Rocco]

Are your valves hard to turn or one hard to turn than the other? When I would vacuum a large amount of leaves, small twig, or a pair of clear goggles once they would get stuck at the valve. Luckly for me I have Jandy valves that I can unscrew and take out to remove any debris.

I am unfamiliar with butterfly valves but a quick google search makes me believe that you will not be able to remove them. However if they are hard to turn it could mean something is there.

 

[mas985]

Is the water level mid skimmer opening? Also is the weir door move freely?

Check inside the skimmer to make sure it isn't sucking air.

 

[MasterTinkerer]

Is the water level mid skimmer opening? Also is the weir door move freely?

Check inside the skimmer to make sure it isn't sucking air.

Water level is mid-skimmer and door is moving freely. It is not sucking air... yesterday when I looked into the skimmer, the basket was not seated all the way... there was not enough suction to hold it all the way in. But, there are other times where water flow rate appears to be normal. I haven't been able to figure out why it works differently from time to time.

When I was first filling the pool, I turned on the pump just after the water level got about an inch over the skimmer inlet. It would suck all of the water out of the skimmer, then would fill back up (due to losing suction and the pump having to prime itself again). I turned it off until it filled all the way, but it seems to be still acting the same - sometimes it is pulling at full force and sometimes not

 

[mas985]

Did this start to happen after you had vacuumed the pool with a lot of debris through the skimmer basket?

I've also made my garden hose fit tight into the hole in the skimmer box and flushed water through the line. Water pours out into the pump strainer, but no signs of anything flushing out.

Have you tried the opposite, from pump to skimmer?

 

[MasterTinkerer]

Did this start to happen after you had vacuumed the pool with a lot of debris through the skimmer basket?


Have you tried the opposite, from pump to skimmer?

I didn't try the opposite with water... I assumed that the check valve would stop it (isn't that the purpose of the check valve?)

But I did the opposite with the air compressor as mentioned.

And I tried to vacuum, but it wouldn't work properly because of the continued intermittent suction



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[mas985]

Why do you have a check valve on the skimmer line? Is the pad equipment elevated above the pool?

 

[MasterTinkerer]

Why do you have a check valve on the skimmer line? Is the pad equipment elevated above the pool?

Yes. I'd say roughly 5' in elevation change as a rough guess


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[mas985]

Ok, then the only way to back flush would be to remove the check valve cover and do it through that way assuming that is the type of check valve you have. This is why a standard two valve is a better choice for priming support.

 

[MasterTinkerer]

Ok, then the only way to back flush would be to remove the check valve cover and do it through that way assuming that is the type of check valve you have. This is why a standard two valve is a better choice for priming support.

assuming the check valve is working properly - yes... will I damage it if I try?

As I said, I could blow air past it... that is why I was thinking to drain the water level. If there is something stuck in there, perhaps I can't push it with just the air as long as the water is in the line. I've also considered trying to get a pipe to fit down into the skimmer hole that is long enough to get it up over water level.

 

[mas985]

assuming the check valve is working properly - yes... will I damage it if I try?

I forgot to mention that is would be a good time to inspect and make sure it is working. But you shouldn't damage it if you are careful prying open the lid. I use a narrow putty knife. When you put it back together a little pool lube on the o-ring will help keep the air out of it.

As I said, I could blow air past it... that is why I was thinking to drain the water level.

Yea but air has virtually no mass so unless the blockage is 100%, it won't do any good. Water flow can help push out any debris in the lines.

 

[MasterTinkerer]

I finally fixed the problem... there was a sweetgum ball stuck in the line. I ran water backwards thru the system (per mas suggestion). It did not make the gumball come out, but must have dislodged it... when I ran air back thru it, it came flying out.

(I put a piece of pvc down into the skimmer hole so that I could make it open to atmosphere - simulating a lower water level)

A whole bunch of hill-billy engineering, but happy to report that it worked!

Thanks for the help


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[mas985]

Good job