Plaster Crumbling In-Ground Spa

[BoombaMon]

Hello everyone, below are my most recent test results. Bought our house about 6 months ago and noticed the plaster in the spa is crumbling off. The walls are super rough, and when you run your hands along it lots of plaster comes off. There are a couple small areas where the rebar has rusted through.

I know this will need to be fixed one day, but for now the spa holds water just fine. From a chemical perspective, do I need to raise my calcium hardness to combat this issue? PH was historically really high and I've brought it in check since buying the house.

Nov 8, 3:58 PM
2.0 FC
7.7 pH
50 TA
230 CH
84 °F TEMP
-0.25 CSI

 

[ajw22]

Once the plaster is crumbling adjusting the water chemistry will not make any difference.

If you can see rebar rusting you should replaster sooner rather than later or the project may cost you more to fix rebar damage.

What is your CYA?

Get a better test kit - Taylor K-2006C or TFT Test Kits

 

[BoombaMon]

Once the plaster is crumbling adjusting the water chemistry will not make any difference.

If you can see rebar rusting you should replaster sooner rather than later or the project may cost you more to fix rebar damage.

What is your CYA?

Get a better test kit - Taylor K-2006C or TFT Test Kits

Last test at the store, CYA was 25.

 

[Dirk]

Where exactly is the rebar, or its rust, visible?

It's one thing for end-of-life plaster to be rough, even flaking off. But that plaster is supposed to be the finish coat over the original concrete shell. And the rebar is supposed to be well-encased in that shell, some number of inches behind the concrete. Even if all the plaster fell off, you still shouldn't see any rebar, not even close.

So either something else is rusting, or you've got bigger problems than plaster.

Best case scenario, your plaster is done, and putting off replacing it, or trying to "slow down the inevitable," is only going to reap a really bad spa experience. Prices don't tend to go down, so putting it off will likely only cost you more, and that's if, as Allen points out, you don't get even more damage to the rebar.

It's possible, since the concrete shell is not watertight, that water is getting all the way in to the rebar, and the rust is leaching back out. But that just means your pool water is eating away your rebar. So the rebar may be embedded in the concrete like it's supposed to be, but the compromised plaster is no longer keeping the water away from it.

Anyway, I was just curious if you can actually see the rebar, or just rust stains.