Scale, I need help please

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needsajet said:
The videos are really helpful, thanks. Brian needs to have final say here, but I think that's pump cavitation and not something you want to allow to happen.
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Good news is it only happens if I pull directly from that valve which is basically never. I do use it once in a while to vacuum with but even then I never adjust the valves enough for that to happen. While all the valves are open, if there's any cavitation or air at all it's not visible to the Eye. The basket is pure clean water unless I pull from that valve primarily. That said, there may still be enough air, even though I can't see it, to be causing me problems at the salt water generator I presume. The new cell is currently on and generating so it won't be long until I know. Scale begins to show up basically after the first day then accumulates the following days. I'm hoping the new cell makes a difference, if it does not I will shut that skimmer off completely and see what happens. I'm also still trying to get my TA to drop but it's being very stubborn currently still at 95 to 100. I say 95 to 100 because at nine drops it is just about to no change, the tenth drop has a slight change where before it was profound. Anyway once I get it down to 90 or below I will add borates as well. I just want to do one thing at a time so I can identify the problem, that is if I can identify the problem.
 
Cavitation. If there was a leak, there would always be air being drawn in because it's the path of least resistance.

Run the pump with that skimmer isolated at 1200 rpm and see what happens.

Now run the pump at a high speed, skimmer isolated and restrict the return line as much as possible. Does the same thing occur?

I can not run my 2" wall suction line by itself at any pump speed above 1800 rpm. The same thing happens if I isolate a skimmer when there is a lot of debris in the basket.

These pumps move a lot of water and a 1-1/2" pipe on a long run just doesn't provide enough water. Having many returns with low resistance makes this issue even worse.
 
I am away from the pool right now but will try this as soon as I return and let you know the results. I really appreciate all the help, thx all.


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No, that is not pump cavitation. That is a simple air leak. There is likely blockage in the skimmer line and when you force all the water through that line, it creates very high suction in the pump basket area which then starts leaking air.

What happens to the filter pressure when you are on one skimmer vs the other?
 
The pressure at the filter remains the same on all valve configurations except when I go to the problem skimmer only, it drops to zero immediately. As soon as I open any other valve the pressure returns.


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That just means that skimmer is blocked. Have you tried a backflush in the skimmer line (sorry I'm too lazy to read through all the posts)?
 
OK at 1200 to 1400 RPM it seems to be pretty good, above that I start seeing air bubbles and by around 1700 it's obvious. Pressure is at zero at all times. I have my pump set on schedule running at 2200 RPM and the pressure sits around 5 psi, if I go to Max 3400 RPM pressure goes to 12 psi. This filter as always maintain a low PSI, and from what I have read and according to the manufacturer that is normal for this filter. In all valve configurations, if I have the pump speed below 1500 there will be no pressure at the filter. They are brand-new elements a couple of months ago. Any way to be certain between air leak and cavitation? If there is a small plug in the line, would that do this or is it a crack pipe if it's a air leak? The way my landscaping is, it would be a nightmare to dig up the line.


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Can you hear sound on my videos? I can't and I'm wondering if you can. Is that normal?


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Any way to be certain between air leak and cavitation?
Click to expand...
Yes, the sound. First, you don't see cavitation bubbles since they only survive in the impeller which you cannot see. Second, cavitation sounds like pebbles being pumped through and your video sounds nothing like cavitation. Third, cavitation is impossible at such low RPM.

If there is a small plug in the line, would that do this or is it a crack pipe if it's a air leak?
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Yes it would. Since the pressure is much lower with one skimmer over the other, that is what indicates blockage. Back flush the skimmer line and see if you can't remove the debris.
 
Just so I'm clear, it sounds like you're pretty confident it is not cavitation but a likely a blockage not a busted pipe? Also here's a silly question, how do I backwash the skimmer line do I just put a hose in there? I'm not sure how else to do it. Not sure how to pressure it up, and also how much pressure is safe without damaging anything?


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Set the valves for that skimmer only, wrap a hose with a wet rag and put it in the pump basket inlet. Try to seal it as best as possible and turn it on full force.

Again, because the pressure drops with that skimmer and not the other, that is blockage. A busted pipe would leak air but would have about the same head loss and pressure drop as the other skimmer line.

Now that is not to say the line could not be crushed. That would behave the same way. Do you know if the lines are flex to the pool?
 
I do not know, I am guessing the pool is 9-10 years old and I've only owned this property about six months. All I know is what is visible to the eye above ground which is 2 inch PVC pipe. I will try to back flush out line and let you know how it goes. Hopefully there is no check valve in line to keep it primed because of the elevation difference.


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One more video just to be sure you hear it clearly.....I up the pump to 2500 RPM. I will send another showing how it acts at a lower rpm going up on a separate post.
https://vimeo.com/175883135


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There is a little sound of cavitation but it doesn't really matter because cavitation and air leaks are caused by the same thing. Blockage in the suction line. You would never see cavitation bubbles in the pump basket so you are seeing an air leak.
 
OK, unfortunately as I thought there appears to be a check valve be in that line. It fills up immediately and I'll let it sit and it does not lose anything. Good news is, the cold well water felt good all over me in this hundred degree weather. Is it possible it's the check valve itself causing this problem? That is of course assuming there is a check valve, but I would think if it was debris it would leak back some? I tried packet it off anyway, my wife was watching out the skimmer and seen absolutely nothing, and I could not get it to pack off completely although I tried.


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One other thought, if there is a check valve, where would it normally be? Right under surface or close to the pool?


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Thanks, once it cools off a bit I may dig a bit to see if I can find it. No way to back wash the line with it in place. I don't know what rocket scientist decided to concrete flagstone where the lines enter the ground, but that will have to be carefully busted away before I can dig down. I can understand and appreciate the pad for pumps and filter but have no idea why they encased the lines going down in the ground. At least it is separate from the pad for pumps and filter. If I do not get scale with the new cell I may not do anything. As long as I don't isolate that skimmer it is not a issue and still works at pulling debris into skimmer basket. If it is the cause of the scale them it is a different story. I know this pool used to be on a SWG..... I'm wondering if this is the reason they removed it.


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