Chlorine Wash vs Acid Wash

ti_chris

Active member
Apr 30, 2017
33
San Jose, CA
Pool Size
24000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi,

I've been noticing over the years that my pool has been getting larger/darker algae stains that are simply not going away. My first attempt to get rid of it of course was to SLAM the pool (15ppm Cl, 30 CYA, 7.5pH, 370Ca) for 24 hrs with heavy brushing every 6-12hrs but that didn't get rid of it. I've left some CalHypo on the floor of the pool and that easily managed to clear out the spots after leaving down there for long enough. The problem now is that I can't exactly 'leave' granular chlorine on the walls of my pool to also clean those out. To double confirm what I thought it was, I looked at my skimmer which had some stubborn algea stains in the grout. Despite my best effort during the SLAM process, no amount of scrubbing could get rid of it all. However once my water level was low enough, I tried a 4:1 10% bleach solution and that got rid of the stains right away with minimal brushing. So I'm pretty convinced that I'm dealing with algae stains that I'd like to get rid of.

I suspect that it's also making maintenance harder than it should since having any algae in the pool promotes having more algea and it's most likely making any chlorine lapse bloom more than it should. Sadly the tube on my Stenner pump broke this weekend (no big deal), but that means that my pool was with virtually no chlorine for 24hrs since the temperatures were over 100°F this weekend and I was left with a nasty bloom that I now have to SLAM & cleanup again. Is my assumption correct that the stains are probably contributing to a speedier algae problem?

My second question was around acid washing vs chlorine washing. I was wondering if anyone did the job themselves. It doesn't look very difficult to drain the pool, spray a mix of chlorine and brush away the stains (PS: I know that my pool is well above the water table through a geo test). My main thought however is that I wouldn't want the mixture to collect in the drain and damage the pipe so perhaps I'd want some kind of way to seal off the main drain temporarily to minimize the damage but I'm not sure what I would use to do that. Maybe an upside down bucket filled with water and with a rubber seal if I can find one that fits? I'd also be curious to hear what chlorine concentration is best to use for this.

My third question is around acid washing vs chlorine washing. My pool's calcium level was too high a few years back to the point where I've had to purchase around ~50 pumices and burn all of them up with elbow grease to clean the tiles. The pool surface is pebble tech and I don't immediately see any calcium deposit signs there. The underwater tiles also dont' show any signs of calcium deposit (only the waterlines had some). Would I be better off doing an acid wash (I'd probably want to get that done professionally vs doing it myself at that point since it's probably harder on the surface) or should I just stick with a chlorine wash?

Thanks for the help as always.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,893
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
No doubt you have algae staining. You might have been doing a short SLAM Process, but even if you passed all 3 criteria, the staining will take much long with an elevated FC level. Not just a day or two. So if you aren't too worried about calcium scale, that's an option. Now if you elect to drain the pool and spray it down directly with chlorine and clean it that way, you can. Just depends on how much work and water you want to go through. A simple drain plug should be sufficient to keep residue from going in there. Again, the acid wash should only be done if needed since it removes a thin layer of plaster or supporting material. If you're not comfortable with that process, I'd leave it to the pros. Hope that helps.
 

ti_chris

Active member
Apr 30, 2017
33
San Jose, CA
Pool Size
24000
Surface
Plaster
Chlorine
Liquid Chlorine
No doubt you have algae staining. You might have been doing a short SLAM Process, but even if you passed all 3 criteria, the staining will take much long with an elevated FC level. Not just a day or two. So if you aren't too worried about calcium scale, that's an option. Now if you elect to drain the pool and spray it down directly with chlorine and clean it that way, you can. Just depends on how much work and water you want to go through. A simple drain plug should be sufficient to keep residue from going in there. Again, the acid wash should only be done if needed since it removes a thin layer of plaster or supporting material. If you're not comfortable with that process, I'd leave it to the pros. Hope that helps.
So if I'm understanding correctly, you're saying you can SLAM the pool for multiple days to get rid of it? How many days would I have to sustain the high FC levels if that's the case? So far levels have been > 12 for ~48hrs. Or is this not really practical and it would be best to empty/clean?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,893
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
So if I'm understanding correctly, you're saying you can SLAM the pool for multiple days to get rid of it?
Not exactly. Stains will take a while unless they are accessible for direct spray like you did before. In this case, if you don't have an active algae growth requiring a SLAM Process, it's a cosmetic issue. You don't have to take the FC up to SLAM level, but perhaps about halfway or so for a while. The elevated FC level combined with regular brushing should help to take effect. It's not an immediate process, but depending on your time and resources might be an option.
 

ti_chris

Active member
Apr 30, 2017
33
San Jose, CA
Pool Size
24000
Surface
Plaster
Chlorine
Liquid Chlorine
Not exactly. Stains will take a while unless they are accessible for direct spray like you did before. In this case, if you don't have an active algae growth requiring a SLAM Process, it's a cosmetic issue. You don't have to take the FC up to SLAM level, but perhaps about halfway or so for a while. The elevated FC level combined with regular brushing should help to take effect. It's not an immediate process, but depending on your time and resources might be an option.
Got it. Thanks for the help. I'm thinking an empty/clean/refill may be cheaper at a later time when I have to refill the pool anyways due to high CH.
 
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