Rust stains in concrete, mesh showing through?

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Rust stains in concrete, mesh showing through?

Postby Cayra » Tue 23 Jan, 2007 03:27

I have a seven year old concrete pool. I have just noticed three pairs of small rust colored dots in the shallow end. I suspect this is from the iron mesh in the pool beofre the concrete was sprayed on. They feel smooth so I don't think the mesh is showing through but must be near the surface

Is this going to cause any structural problems?? I can't afford to have the pool resurfaced and even if I could we are not allowed to refill polls in Australia at the moment due to a drought causing water restrictions

I can live with the stains ... I'm just hoping it wont cause bigger issues

Mike in Tampa
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Postby Mike in Tampa » Tue 23 Jan, 2007 07:19

try turning off your filter and let the water settle for 5 minutes or so then sprinkle some pool shock directly over the stain and let it set for a minute and brush.

it worked for my stains that turned out to be discoloration from debris that had settled on the bottom.

Postby Guest » Wed 24 Jan, 2007 09:30

if it is a piece of rebar rusting through, it will not cause any structural problems, just cosmetic. to repair without replastering the entire pool the pool must be drained below the rust spot, grind away the plaster and gunite to expose the rebar. trim the rebar, spray with rust inhibitor and patch with cement or plaster. The patch will not match the rest of the pool and sometimes is just as noticable as the rust itself.

Postby Guest » Thu 25 Jan, 2007 21:56

That's what it appears to be to me


Good to hear it's just a cosmetic issue

I must admit when they surfaced the shallow end it looked a bit thin

I've actually found 5 pairs of rust dots now... hope there's nit going to be too many more... they are very small
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Postby Pool Owner » Fri 26 Jan, 2007 10:29

Cayra, since these are “dots” you may want to think back some. Has there been any fertilizer used near the pool over the last few weeks/months? Fertilizers with iron can rust and discolor the plaster. I would think that this is a more likely problem unless the “dots” are real close together. There are too many variables for rebar to rust through over a large area at the same time. If it is fertilizer, you will probably want to do a complete water chemistry check, especially for metals and phosphates (which could “feed” algae) to address any other issues.

While probably less likely and dependant upon your location, another possible reason for “dots” could be from steel shot from a shotgun used in hunting.

Do not panic with this paragraph but if the stains do come back in the same place, it is my understanding that “standard” plaster used over the last few decades has changed in its chemical makeup to address environmental issues and unfortunately does not last as long as it did when my parent’s pool was built in the 1950’s. I have heard that “standard” plaster can start to have problems around the ten-year mark, which you are approaching. If it does turn out that you are getting a general breakdown of the plaster’s ability to remain waterproof over a large area you may seriously want to consider replastering (or painting) the pool to prevent significant (e.g., structural) damage. Isolated rebar rusting can easily be spot fixed but widespread plaster failure and rusting of the rebar throughout a large area should not be allowed to continue.

Good luck in getting your pool back into ship shape. I have found a good reference book helpful. Check out my blog for a few book simple reviews.
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