How to perform an acid wash?

DIYconvert · May 10, 2013

Hi All,

I'm looking for a good set of instructions and best practices on how to perform an acid wash on the plaster surface of my pool. I couldn't find a good, relevant post. I found some information on the internet; however, none of it is as complete and detailed as I usually find on this forum. Can someone direct me to a good post? I think this would be a good "How To" sticky in the Pool School section.

Thanks!

aquaman · May 19, 2013

I was so hoping someone would have answered this! There is a Youtube link that gets the overall idea

http://www.youtube.com/watch?v=OMj7KNKCkS8

DIYconvert · May 23, 2013

Thanks for the reply. Yes, I watched that video, and several more. I think a sticky would be in order for this subject. In my research thus far I've gathered several very important tips, instructions, warnings that are not mentioned in any of the videos or simple instructions on the web.

From what I can tell, performing an acid wash seems simple enough; however, there are several "gotchas" to watch out for. Examples include:
- Acid vapors can kill, always have a second person around and make sure your respirator filter is rated for Acid Gas (AG), Most sold in hardware stores for painting only handle Organic Vapors (OV). BTW, you can get an AG rated filter at Grainger.
- When washing the shallow end, the river of acid runoff to the deep end can cut a channel down the middle of your pool floor.
- Draining your pool completely in hot weather can damage your plaster.
- There is an additive you should add to the acid mixture to lessen the vapors. I don't remember the brand name; however I heard from a local pool service that Dawn dishwashing liquid works well too.
- The preferred method of application is via a watering can; however, in watching some of the videos the sprayer method seems to be effective.
- The time you should leave the acid on the walls before rinsing was anywhere from 30 seconds to 2 minutes. The longer you leave it on the thicker the layer of plaster you will be taking off.
- The maximum strength you should mix was anywhere from 50/50 to 75/25 acid/water. Rather than higher strength it seemed that you should do more passes instead.
- A submersible pump is handy for getting the acid runoff out of the bottom of the pool. You can rent one; however, you may be able to buy one for the cost of a two day rental (check out National Tool and Equipment for an inexpensive pump).
- Check local laws, in some areas you can be heavily fined for pumping the acid runoff to the street.

aquaman · May 23, 2013

Great information that would be an excellent part of a Pool School document!

I had spot cleaning needs (corners and bottom of hot tub) and accomplished it with a 1:5 dilution and the use of some 80 grit sand paper on a palm sander AND my power washer.

WVUTampaAlum · May 23, 2013

Why do you want to acid wash your pool?

DIYconvert · May 25, 2013

When I had my pool re-plastered, it soon started to show signs of white spotting due to improper plastering techniques. Over time, the white spots grew and became more and more porous causing stains from algae and the tannins in leaves to set deep into the plaster which cannot be cleared by a standard shock process. I heard an acid wash can make your pool look like new; sort of like a chemical peel treatment performed on the face to make the skin look fresh and new. However, after further study I realized it's not a good idea to acid wash a pool that already has compromised plaster. So, instead, I just power washed it and did a bleach wash. That helped a lot; not as good as an acid wash but good enough for now.

Another reason for performing an acid wash is to clean up the algae spores that can get stuck in the plaster if you have a pitted surface and you are trying to recover your pool from swamp conditions. You can spend a lot of time and money on bleach trying to get a pool from green to clean if you have a pitted surface. And you may not get all those pesky spores. They can sit around hiding and spark a new algae bloom if your chlorine levels drop for too long. An acid wash can be done in a day and cleans the surface of all algae. It does, of course, require you to drain you pool, so you want to weigh you options before going that route.

WVUTampaAlum · May 26, 2013

I would not recommend doing a direct acid wash without getting serious professional opinion on it.

That said what you may want to look into which is aggressive but not as much as direct acid wash is 'California hot wash'. I have a nearly black plaster pool . Had the pool builder mix charcoal and french gray plaster. It came out amazing but after they were done I could see light /dark lines in the finish. This was from the initial acid wash. They told me to brush it 2 times day for a month. I saw this going no where after 2 weeks and started heavy research on it. What I found was idea of putting a bunch of acid into the pool. They were not familiar on it and very resistant. I hink for my pool we did 4 or 5 gallons in the pool for 24 hours. You need to then counter act the acid with I believe borax. You run the risk of etching anything metal. I will tell you our finish came out absolutely amazing. There were no lines anywhere.

Again this is very aggressive but read up heavy on it and understand exactly what you are doing.