Scale, I need help please

[Lykly]

zappaan, thanks for the input. If you go back to page 8 of this thread you will see the valve configuration. I put a variable speed pump on a couple of months ago, and everything from 6 inches above the ground up is new plumbing. Unfortunately where the PVC 2 inch lines come up, they are encased in flagstone. This is separate from my cement pad my pumps sit on so it shouldn't be that hard to break up. Based on that skimmer line providing water to the pump at least enough to operate, the fact that when I tried to backwash it and it would not let anything past the other direction and it also stayed full of water, I have to believe there is a check valve. If it was so obstructed I could not get anything at all to pass backwards, I find it difficult to think it would flow to the pump as much as it does. If there is indeed a check valve close to the surface, then I would not be so nervous about running a snake. Is it possible that a 1.5 inch PVC line 40+ feet just does not give up enough water by itself? Obviously it gives up enough water for the other skimmer and floor drain intakes, but they are probably twice as close to the pump.


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[Zappafan]

Understood. Well if you ran the snake backwards you should hit the disk on the check valve and the snake shouldn't get hung up coming from that direction and will save you from digging it up like pooldv said. Line sizing is an engineered science all to itself I have very little experience with it. The goal is to keep your pump from getting ruined due to cavitation.

 

[Lykly]

OK, I misunderstood pooldv.... I thought he meant from the skimmer going to the pump. I agree going the other direction that should tell me if there is a check valve there and how far it is. If I do hit something, I won't get very western with it I will stop. Hopefully if it's just a few feet I can just dig it up and then I can snake the whole line hopefully. I really appreciate the guidance. Prevents me from making major mistakes.

On another note, I do see slight scale, but nothing like it was producing before. I need a few days to find out if this is a residual scale or if the cell is still making a small amount, but either case it's way better than it was.

Now my biggest concern is why my TA and CH rose unexpectedly. From what I understand there's no way for that to increase without additional water, correct?



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[needsajet]

As far as trouble-shooting the scale, could you set your skimmer valves and main drain valve so the pool works to your satisfaction, but there is no evidence of pulling air into the system. Then leave it for a week or so? Maybe we can confirm or eliminate the introduction of air into the SWG as a possible contributing factor.

If you need to vacuum, only reduce other suction valves to the point that no air is introduced.

Could you give the Post # that shows your equipment pad, valves, etc.?

As far as a couple other things that came up, check valves are mounted near the pump so they can be serviced. As long as air can not enter a suction line, the water can not get out, so a check valve near the pump prevents the line from draining when you take the pump strainer lid off. It's OK to throttle suction lines as long as you don't starve the pump or throttle it excessively. Throttling an individual line is just shifting flow from that suction line to the other suction lines.

 

[Lykly]

157, 158 and 159 shows a couple videos including elevation, the pump problem, and a picture the valve configuration and equipment. Just to let you know, When I remove the pump basket cover it will drain, but it is because of the vacuum that is created going back to the pool returns through the filter. If I shut everything off, it will hold prime is long as the lid is on the pump, But as soon as I remove it the water will drain (get sucked) through the filter back into the return lines to the pool. This is because the pump pad is probably 8 feet above the pool.


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[Lykly]

Just so I'm clear on the term throttling, you're talking about manipulating the valves to get better suction from a certain line? The only time I get any cavitation is if I try to pull from that one skimmer I'm having trouble with otherwise it seems the other lines can give up enough water to satisfy the pump. When vacuuming, I normally close the floor drain and then let the pump get its water from both skimmers, and I switch between them for vacuuming. I have a 25 foot vacuum hose and it is about 4 feet short of allowing me to do that shallow wading pool otherwise I would just use the strong skimmer for vacuuming. In the past, that wading pool is where much of the scale settled out.


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[proavia]

I don't feel like re-reading this entire thread and can't remember if you already did this - but.... In this picture from post #159 - have you checked for air leaks at both sides of the 90° elbow fitting of the skimmer in question. The elbow at the lower left is for sewer drain use - that's why it has a sweep to it. These type fittings have much thinner side walls and shouldn't be used in pressure situations (probably not here for suction either). The fitting is mis-aligned at the end nearest the black valve. Maybe the fitting is somehow compromised or one of the two joints is leaking.

... Two lines coming up into one valve are from the skimmers, the left one being the problem, the single line that joins them is the floor drain. ...

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[Lykly]

proavia, thanks for noticing that and explaining it, I had no idea they used an improper fitting. I just went out there and checked and as far as I can tell I cannot see or hear any leak or indication of a leak. The picture you seen seems to exaggerate the misalignment a bit although it is misaligned as you can see in pictures I will attach here. Also in one of the pictures you can see the 2 inch collars near the ground level, from that point up all the plumbing was replaced very recently, and this problem was occurring before the lines were changed out. I changed everything from near the ground up when I put the new variable speed pump on. I will have to ask the guy who did it why he used a sewer plumbing fitting on the configuration. I do know that the lines coming up in the fixed flagstone are not perfectly straight up-and-down which caused some problems, he may have had to use that fitting I'm not sure.


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[bdavis466]

That looks like a SCH 40 sweep to me. Is that what is says in the writing on the collar?

Those types of sweeps are the only ones I ever use and are rated every bit as high as a standard SCH 40 elbow (typically near 300 PSI). If its a DWV sweep then thats not the correct fitting to be used.

 

[Lykly]

This is what it says, opposite sides from each other on the same end. Not sure what it means.

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[bdavis466]

That's sch 40. No issues with that at all

 

[Lykly]

Thanks for confirming. I don't think it's leaking, at least there's no indication, so it appears the problem is still in the skimmer line.


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[pooldv]

I was thinking snake from one or both sides. Good points about the snake possible getting hung up in the check valve.

You can spray some shaving clean around the fitting in question to see if it gets sucked into the pump basket.

 

[needsajet]

I'm going to stay off the leak detection aspects, because I think a 3 HP pump sucking from one skimmer with 8' of lift and potentially a small diameter pipe could be cavitating inside the pipe. I actually don't think it's blocked, though certainly it may be, but I think if it was blocked very much at all, it wouldn't have given you the tons of vacuuming suction you mentioned early on when this aspect came up.

In the meantime, if just chasing the scaling issue, we can eliminate the air getting in the system and hopefully rule that in or rule it out, as part of the "SWG creating scale" problem.

Throttling means slowing down flow. So in the case of a valve it means turning it to partially restrict flow. So for example, leaving both skimmers wide open, and partially closing the main drain valve, means you have throttled the main drain.

So what I was getting at, was to put the valves in whatever positions works for normal operation of the pool. (probably skimmers wide open and main drain throttled a fair bit, which causes more of the flow to come from the skimmers). Main thing being, set the valves so no air accumulates in the pump basket.

If during a one-week test period you need to vacuum, don't set the valves at any time or in any way that causes air to accumulate in the pump basket.

I'd actually suggest you never set the valves in a way that causes the air to appear in the pump basket.

Just in case it's extra comfort, I also have schedule 40 (called PN 9 down here) sweep 90 elbows.

For some reason, I'm having computer issues seeing the pictures (some are fine, some just X's, some the bottom half is grey!) so I'll take a look later.

 

[Lykly]

Thanks needsajet for confirming what throttling the valves mean, I understand now. I also understand your reasoning about a 3 hp pump and feed restriction from the line. Before I get back on the scale topic I just wanted you to know that the other two lines have no problem supplying the feed, and my old pump which was one horsepower also had the problem with the same skimmer. Also from that line it starts pulling air at only around 1500 RPM. That said, as long as it's not causing me scaling, I'm not that concerned about it because it still does the job.

As for the valve configuration, I do exactly what you suggested, I leave both skimmers wide-open and throttle back the main floor drain probably by 50%, the pump does not at all struggle for water and there is no air in the basket. I can already tell this new cell does not put off nearly as much scale residue as the old one did. There is a small amount of scale I can see in the pool, but I had five grandkids in it all weekend and I can't tell for sure if it is residual scale or new scale, but less for sure. Tomorrow by after work, any residual scale will have had time to be deposited into the pool and settle out, so I will not touch the valves and vacuum tomorrow after work. Then I will just monitor the chlorine level and adjust the SWG if needed as it appears to be making more chlorine than my old one did at the same settings. I am hoping if I can power back the SWG it may reduce the scale even more. For now I won't touch anything.



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[pooldv]

Yay for grandkids in the pool all weekend! That is what we are a here for!

Just for the record, Mark is the resident pump expert. He knows stuff about pumps and hydraulics that we don't even know there is to know. If he says the skimmer line is clogged then I'd bet a buck or two that it is clogged.

 

[Lykly]

I was thinking snake from one or both sides. Good points about the snake possible getting hung up in the check valve.

You can spray some shaving clean around the fitting in question to see if it gets sucked into the pump basket.

Thx pooldv, I learn something here new every day it seems. I will try the shaving cream just to be sure there is no leak at that union.


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[Lykly]

I just thought of something and was wondering if you think this could be contributing to my scale problem. I have a Kreepy Krawler pressure side cleaner. It has a 1.25 hp pump, and gets its supply of water just past the salt water generator. I know it uses a fair amount of water, could this draw be contributing? You can see from the picture where it gets its water from just passed the salt water generator and the cell. This kicks on and runs for 2 1/2 hours just about the same time the SWG starts for the day. I'm just wondering if that pulling water could be causing some turbulence at the sale? Here is the picture of the set up.

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[pooldv]

I don't know the answer to that but 2-1/2 hours is a lot to run. I used to run my cleaner an hour a day and then switched to an hour a few times a week and now I don't use it at all because it annoyed me a few times too many and I threw it into the yard . I just use the leaf rake and brush to the main drain.

 

[mas985]

I just thought of something and was wondering if you think this could be contributing to my scale problem. I have a Kreepy Krawler pressure side cleaner. It has a 1.25 hp pump, and gets its supply of water just past the salt water generator. I know it uses a fair amount of water, could this draw be contributing? You can see from the picture where it gets its water from just passed the salt water generator and the cell. This kicks on and runs for 2 1/2 hours just about the same time the SWG starts for the day. I'm just wondering if that pulling water could be causing some turbulence at the sale? Here is the picture of the set up.

Pressure side cleaners don't use all that much water. Mostly pressure rather than flow. Scaling is about chemistry. Nothing else. Keep your CSI between -0.25 & -0.5 and the SWG should not scale much.