Erosion on underside of waterfall ledge: recommended sealant?

[Hot_Rod]

1) I am having erosion issues underneath our large waterfall's grotto ledge. Wondering if there is a good product to seal this? I have read of erosion from salt for grotto/waterfall but our pool is not SWG, so I guess this is just from the spray? There are chips 1"+ flaking off, never mind the gray concrete type powder this leaves in the pool so would love to seal it in, perhaps this offseason. Pretty much any time I go to brush there is a good amount of powder and debris underneath.

2) Also - should I apply similar/same product to the waterfall path itself (the top side where water flows), for this big waterfall plus other little falls?

This pool and waterfall built 2010 and no maintenance done to waterfall since to my knowledge....Thanks!

Photos below show waterfall design, closeup of front of ledge from below (you can see see where old finish separating) and from underneath in the grotto (old finish worn off and remainder all powdery to touch)

 

[ajw22]

That ledge looks like a poured concrete slab and the concrete is eroding. You can try sealing it with a concrete sealer but I think the damage is done. A sealer is not going to hold it together as it is deteriorating. Long term the repair is to lift off the rocks and build a new ledge.

Let's see what @jimmythegreek says. Or @Rich D

 

[Rich D]

Do you know what type of rock that is? Is the upper rock shelf sowing the same issues? Strange how the most damage seems to be in a area that does not see much of the pool water. I know the underside of my shelf has a lot of condensation on it but never really sees any pool water. Have you changed anything with the way you maintain the pool water? Is that white ring on the other rocks something new? Perhaps a rock guy might be able to help @MinerJason .

This is not my area of expertise, However I really do not think a sealer will do much without blasting and chipping off all the loose rock and getting back to some solid rock.

 

[jimmythegreek]

Theres salt in every pool, you may have equal levels to a salt pool at this point. Hard to say that's real limestone, it looks like precast faux slabs by the pics. I agree sealer is probably not gonna do much at this point. In the pic we see the yellowish color faded to a whitish grey. Does it appear to be a top coat of color that's faded or is the grey over the yellowish color like a build up?

 

[Hot_Rod]

Hi – appreciate the replies and hope this info can help.

• No idea what type of rock the slab is - We bought the place in 2017 and it was built in 2010. I have all paperwork but nothing specific on waterfall slab content. Only mention of any concrete is the shotcrete gunite for pool.
• On color: if anything it has always looked up close like two slabs melded together like that mid photo. The top yellow part chips away some but has not worn to a powder, and is yellow too underneath the chips, but the bottom half is all gray including underneath the bottom chips. That two-tone color– yellow top, gray below - has been there since at least 2017.
• I have never tested for salt levels, only use the TF-100 kit so not even sure how? Did not realize I could (should?) do that without having SWG.
• White ring not new, has been there last 2 years – from hard water and calcium I figured. I had the water levels a bit lower when I took this pic to do some waterline spray + scrub.
• Nothing has changed in water chem treatment in last 4 years – use bleach along with CYA and Muriatic for pH. Levels have been good this summer and nothing out of ordinary.

Overall when we moved in some of the underside was flaking off here and there but nothing major, but I feel like it has moved from flakes to more powder erosion now, almost like the underside’s ‘top coat’ is largely gone (like you can see) It’s really weird, and I too have been baffled at how the most wear is not at the edge. Or at least why the front is flaky and the back hs had more wear and is powdery.

I might have the original installer company out to have a look at it. We are probably due to get a full refinish/replaster of pool at some point in next year or two so may as well get them to quote and give some ideas on this as part of that. But I was certainly hoping there was some DIY treatment (sealant etc) I could use to stop or slow this, as I’m willing to apply it – or chip/sand away some of bottom then apply. Thanks all for your input.