Flaking plaster

[Xentex]

This is my first season owning an 18 year old pool in a house we bought this spring.

Pool had been unused for 3 years, was a disgusting green swamp, and we had it drained and acid washed. Came out looking great. However...

When the guys were draining and cleaning it the business owner pointed out something he said was kind of unusual. He said the pool plaster looked like it was in good shape overall, but there were places where the plaster was kind of flaking. It looked like somebody put a skim coat on in certain areas, particularly on the stairs. I asked him what to do about it, he said probably nothing. He said more would probably flake off (which seemed obvious to me) but that it probably wasn't worth replastering.

There's clearly a different texture underneath the flakes that come off. It's much rougher underneath. He thought maybe the prior owners didn't like the rougher more sandy texture so somebody put a skim coat on it. Seems plausible to me, but I don't know anything about pools and plaster and all that.

So here's my problem... There's a lot of surface area where this was done, and the problem I've been having all summer is algae just loves these areas. I've shocked and slammed a couple times, but if I miss one day of putting a full gallon of 12.5% bleach in the algae is right back. I'm about to SLAM yet again.

I'm now wondering if part of my problem is I'm never getting the algae fully out from under the flaking areas. There are literally hundreds of places where I can get a fingernail on the edge of a spot where that thin layer of plaster has previously flaked off. If I pull with my fingernail I can pull off more flakes. It's like picking paint flakes off an old wall or fence. These plaster flakes are maybe 1/32" thick. When I pull them off I can see green or black on the underside around the edges. I imagine this is algae that escapes all my scrubbing, and because there's no real water circulation underneath the flakes that are still attached, even my shocking it's getting under there to kill them. I'm wondering if 3 years of sitting as a swamp allowed all sorts of stuff to creep under that flaky stuff, and even the acid wash didn't get under there to kill it.

Is this at all normal for pool plaster? I'm thinking of using a paint scraper to get all this flaking junk off. Or will that make something worse? And how do I know when I need new plaster? What's the process for re-plastering?

 

[Jimrahbe]

x,

My experience has been that you don't normally see anyone just spot plastering a pool. I think that would be unusual.

A normal failure mode for plaster is that it looks ok on the surface but comes loose from the gunite and then starts to determinate. I have had a couple of pools re-plastered and in both cases, the plaster guys went around the pool knocking on the plaster with a hammer. If it sounded hollow they chipped it all out. I could see a couple of bad spots and that is why we were re-plastering to begin with, but I was amazed at the number of spots they found that were not visible before the re-plastering started.. I'd say 25% of the old plaster surface had to be removed.

I suspect that you are looking at a re-plaster job.

Thanks,

Jim R.

 

[Xentex]

Thanks for the reply, Jim.

How thick is the plaster typically? Like, how do I know if I'm through the plaster and touching the gunite? And how does plaster typically fail?

If it has to be redone I'm fine with that. It's just that I had a pool guy looking at it when it was empty a few months ago and he said the plaster looked fine, except where it looked like somebody tried to put a skim coat or something on it.

 

[Jimrahbe]

x,

Plaster is about 1/2" to 1/4" thick... You would think that your plaster guy would know, as I'm sure he has much more direct experience than me...

You can definitely tell when you get down to the gunite.. Plaster has some color to it and gunite generally looks like concrete.

You should post a couple of pic.. If you do, I suspect that you will get more inputs once people can see what the problem looks like.

Thanks,

Jim R.

 

[pooldv]

Plaster fails a number of ways. It can lose its bond to the substrate and come off in chunks. It can slowly etch and dissolve into the water as calcium. It can build up scale to the point that it can't be removed.

But, if the plaster is still on the pool walls then only real reasons why you would need to replace your plaster is if you don't like how it looks or if it is leaking. Otherwise, it is fine to put it off as needed.

I would maintain your FC a little higher, around 10%-15% of your CYA level, and brush those spots a little more often to try to keep the algae away.