What is this orange/rust colored substance in my hot tub? (Rust?)

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M

msykes

0
Aug 18, 2018
7
San Diego, CA
Noticed this strange orangey-colored substance in my hot tub recently. It started out as a bit of an orange smear, but has since thickened quite a bit. It may be hard to tell from the picture but it actually is several mm thick. This picture is from a week ago, and it's even larger now. It's below the water line, and at the seem between the tile and the pebble finish. You can see from the flakes on the seat that it's quite fragile.

I assume this is rust based on the color, but my googling of pool rust pictures didn't turn up anything quite like this. Still, I'm not quite sure what else it might be.

If it is rust, best thing to scrape it off, vacuum it up and seal that crack? I have some Atlas epoxy pool putty, or would something else be better suited?

Thanks!
 

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Welcome to TFP! :wave: If there is rust (iron compounds) to that build up, it's not how we normally see rust present itself. Unless you get your water from a well or have city water with a lot of iron, it would seem odd in your area. Especially if that's the only place in the tub doing it. Perhaps something else leaching out from behind the tile or a combination of the two. You could lay a Vitamin C tablet on that growth to see if it does anything to change the color. If it's hard and you can break a piece off, place it on the grass or in a jar and add a little muriatic acid to see if it fizzles (calcium scale).
 
Texas Splash said:
Welcome to TFP! :wave: If there is rust (iron compounds) to that build up, it's not how we normally see rust present itself. Unless you get your water from a well or have city water with a lot of iron, it would seem odd in your area. Especially if that's the only place in the tub doing it. Perhaps something else leaching out from behind the tile or a combination of the two. You could lay a Vitamin C tablet on that growth to see if it does anything to change the color. If it's hard and you can break a piece off, place it on the grass or in a jar and add a little muriatic acid to see if it fizzles (calcium scale).
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It's definitely not calcium scale (I have a LOT of that from our ridiculously hard water and lots of experience with it), and it seems quite soft rather than hard (breaks off if the water is disturbed).

It's the only place in the tub or pool doing it, and it started only recently.

I have a Costco pack of vitamin C so plenty of tablets around, what would a color change tell me?

Thanks!
 
Looks organic/biological to me. I’d scrape it all off and vacuum it all away. Then lower the water level in the attached spa and inspect that area. Try to clean out that gap as much as possible. Applying a small amount of pool epoxy should be fine. Then just watch the area to see if it returns.

Are you keeping your sanitizer levels up properly? Is the spa getting a fresh turnover of chlorinated water during the day?
 
JoyfulNoise said:
Looks organic/biological to me. I’d scrape it all off and vacuum it all away. Then lower the water level in the attached spa and inspect that area. Try to clean out that gap as much as possible. Applying a small amount of pool epoxy should be fine. Then just watch the area to see if it returns.

Are you keeping your sanitizer levels up properly? Is the spa getting a fresh turnover of chlorinated water during the day?
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Both pool and spa measuring at 3 PPM FC right now... I tend to run a little higher in the summer but it's winter and water temps are low 50's right now.

I suppose what it is might be secondary to what to do about it, sounds like removing whatever it is and putting a little epoxy on is the way to go regardless.
 
First picture - about a week after the original, growing bigger (was out of town so didn't get a chance to deal with it).

Second picture - what it looks like after partially draining the hot tub, most of it just flaked away from the motion of the water, and is now sitting on the bottom of the tub.

With all the buildup gone it looks a lot more like a rust stain.
 

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So it could be a piece of rebar in the concrete shell is exposed to the plaster at that plaster/tile interface. The rebar will rust through that crack and grow out to the water. Iron oxide / hydroxide grows outward from the metals surface and continuously ... never stops until all the iron is gone.

The fix is unfortunate - tile and plaster in that area will have to be removed, the area of the concrete shell will have to be chipped out to the rebar and the rebar cut back. The the area gets sealed up with hydraulic cement and the tile and plaster will be restored. Now it may be that there is just a foreign object embedded in the plaster at that location like a nail or a piece of rebar tie. That can happen easily during the build. In that case, the tile and plaster still need to be chipped out and removed but the it may not require any significant digging into the shell.

Is this a new pool/pool-build or an old pool?
 
JoyfulNoise said:
So it could be a piece of rebar in the concrete shell is exposed to the plaster at that plaster/tile interface. The rebar will rust through that crack and grow out to the water. Iron oxide / hydroxide grows outward from the metals surface and continuously ... never stops until all the iron is gone.

The fix is unfortunate - tile and plaster in that area will have to be removed, the area of the concrete shell will have to be chipped out to the rebar and the rebar cut back. The the area gets sealed up with hydraulic cement and the tile and plaster will be restored. Now it may be that there is just a foreign object embedded in the plaster at that location like a nail or a piece of rebar tie. That can happen easily during the build. In that case, the tile and plaster still need to be chipped out and removed but the it may not require any significant digging into the shell.

Is this a new pool/pool-build or an old pool?
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Ugh - that sounds "fun"!

This is an old pool, not sure exactly when (we are second owners) but about 5-ish years old.

Vitamin C removed most of the discoloration, likely confirming it's rust.
 

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There’s definitely something iron back there. Could be rebar or it could some nail or tie that got embedded in the plaster. My neighbor has a similar discoloration spot show up on her deep end wall about 18” down. Her pool guy did a surgical chip out and replaster (patch) and it went away. Of course he charged her an arm and leg to do maybe a 2 hour job with minimal materials and he made her completely drain her pool which also drove her water bill into the stratosphere. But it worked.
 

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JoyfulNoise said:
There’s definitely something iron back there. Could be rebar or it could some nail or tie that got embedded in the plaster. My neighbor has a similar discoloration spot show up on her deep end wall about 18” down. Her pool guy did a surgical chip out and replaster (patch) and it went away. Of course he charged her an arm and leg to do maybe a 2 hour job with minimal materials and he made her completely drain her pool which also drove her water bill into the stratosphere. But it worked.
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Yeah, the arm and leg is what I'm concerned about! Not to mention it is virtually impossible to get pool people around here to do anything short of build you an entire new pool. Will attempt some band-aid repairs and report back on success and/or failure.

Thanks
 
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Predictably my bandaid fix did not work. Got a quote from a well-reviewed pool repair specialist for $695 for the repair, does this sound reasonable to anyone?

Pool
  • Chip out rotted plaster, tile, concrete and cut out rusted rebar
  • Fill cavity with hydraulic cement and re-plaster with underwater plaster
    material
  • Warranty depends on depth of placement of existing rebar to plaster
o The greater the depth the longer the warranty
o 1 inches depth from plaster will have a 1 year warranty o 2 inches depth from plaster will have a 3 year warranty
- We will drain spa for repair after fill when done.
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Well, I'm not contractor, but that seems to be in the ballpark. Materials probably aren't too expensive, but labor alone will be 2 - 3 hrs I would expect. Maybe longer. Let's see if others have some recent experience with costs.
 
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Yeah, that kind of job is all labor. It’s not a bad price and they may find that it’s not rebar but something simpler like a rebar tie or a nail. Wouldn’t surprise me if it was a an embedded nail given the location as many tile guys will nail trim board into the gunite shell to create a level strip for tile placement purposes. If they remove the board but leave behind a nail or screw, then it will get embedded in the plaster and cause rust stains.

A 1 year minimum warranty is nice too.

Just be warned - no plaster patch will ever look perfect especially when it’s fresh. That area is going to stick out no matter what they do so be prepared for a noticeable blemish to be visible. And it’s not going to be surgical either - when they remove the tile and chip out that area, it’s going to be several times larger so that they have room to work.
 
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