Never ending scale problem (?)

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Bart

LifeTime Supporter
Jan 24, 2010
309
Northern Virginia
I have a gunite pool with a SWG so naturally my pH creeps up. I’ve done the borax treatment which helped lessen the need for acid, but (I think) I’m still having a scale problem.

I’m still getting little “dots” or “lines” (sort of shaped like icicles) on the pool walls. Normal brushing doesn’t remove them, but when I use a kitchen scrubber (which sort of looks like a Brillo pad made out of plastic attached to a handle) they usually come right off. When I’m doing my “brillo scrub” along the walls, white “dust” also billows off. I’m assuming this is very tiny bits of scale that. This “dust” comes off only when I use the brillo scrubber, not when I use the regular pool brush on the long pole.

I guess my questions are:
1. Is this scale coming off?
2. Will it ever stop?
3. What can I do about it? (both the “dust” and the actual scale formation)

Here are my numbers:
FC 4.5
CC 0
TC 4.5
Ph 7.5**
T/A 100
CH 600
Borates 50

**Regarding the pH - - we’re only at the pool on the weekends, so during the week it creeps up to 7.8 or higher and on the weekend I knock it down to 7.2 or so.

What's my next step?

Thanks!!!
Bart

PS - pool is 4 years old
 
Your CH is high, couple that with high pH and scale will form.
Only way to lower the CH is through water replacement.
What is your CYA level?

Also, please add your location to your profile.
 
If you plug all of your numbers into pool math (don't forget temperature) there is a section at the bottom labeled CSI (it is green) you want that number between -0.6 and 0.6 Higher and scale forms - lower and it sucks the CH out of the masonry (among other issues).

I suggest starting to harvest rainwater, it will get your CH down in a hurry. (search for my thread on rainwater harvesting).

Watch your pH VERY closely. don't let it get over 7.5 (but not lower than 7.2), this will help with scale prevention.
 
Fill water and cal hypo shock are your likely suspects for high ch.

Ph will rise in a plaster pool, iirc swg will push it as well ( no coffee yet not sure on swg)
 
Karma -
I think you're right about the SWG pushing the pH up. Half the time I wonder if should just shut it off and chlorinate some other way.

When you say "cal hypo shock" what does that mean?

Another question -- if I did turn off the SWG and chlorinate with bleach for the rest of the season, would that help the pool completely "cure" and stop the scale from returning? Or would the problems return once I turn the SWG back on?
 
the SWG isn't causing the scale - the pH / CH combo is. The key is to add Muriatic acid as the pH creeps up. The age of your plaster is going to play a part as well. I would shoot for a little lower on the front end (7.0 ... not usually recommended but given the time between dosings that should help keep you out of the 7.8 scale danger zone). Also start harvesting rainwater to get that CH down via water replacement.

Cal Hypo Pool Shock adds CL and CH to the pool. If you or a prior owner used this to shock the pool it would drive the CH up. Since CH doesn't evaporate you have to replace water to get rid of it, same with CYA if a trichlor or dichlor shock or puck product was used regularly.

Chris

My thread on rainwater harvesting:
http://www.troublefreepool.com/threads/73339-Rainwater-harvesting-and-TA

My CH was in the 1000+ range before I started - now in the 200-400 range (rainwater brings it down, CH scale goes back into solution and drives CH back up leaving cleaner pool walls).
 
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Thanks karma!

To answer one of your earlier guestions, my CSI is now 0.04 and the pool calculator says it should be -0.22 (if I did it correctly).

For context here are the pool calculator numbers.

Now // Target

FC 4.5 // 5
pH 7.5 // 7.5
TA 100 // 70
CYA 65 // 75
Salt 3100 // ?? Have to check the manual
Borates 50 // 50
Temp = 88
CSI 0.04 // -0.22

I re-ran the numbers while keeping everything the same except for pH which I lowered from 7.5 to 7.2 and then the CSI recommended level went down to -0.46!

I suspect that's an important detail, but I just don't know what it means!!!

Does the current CSI (.04) tell you anything if the current target is -.22?
What does it mean if I lower my goal pH to 7.2 and the target CSI drops to -.46?

Also should I be concerned about my TA being 100 when 70 is the goal? Is that a player in my problem?

THANKS!!!
 

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right now you are GOOD.

Plug in 7.8 or 8 and see what happens to the CSI. You are getting up to the range where scale is a concern. If you control the variables you can keep the CSI in the lower range and subsequently scale won't be able to form.

You could also pull your TA down, that would give you some breathing room if the pH does creep to 7.8 or 8 while you are away. The flip side is with a lower TA the pH is more likely to swing. That will be a balancing act.

Don't sweat the "reccomended" level pool math is coming up with. Know that your desired range is +/- 0.3

To quote Jason:"The great majority of pool owners can completely ignore CSI. As long as you maintain your levels within our recommended ranges your CSI will be taken care of. The main time you need to worry about CSI is when your TA or CH levels are unavoidably high, for example when your fill water is high in either TA or CH or both. Then you need to start adjusting your other levels to keep CSI from getting out of bounds."

Unfortunately you are in the High CH club. once you get enough water replaced your CSI wont be of concern ... it will be "normal" when everything else is normal.

Absolute best bet - replace some water and get that CH down.
 
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