Any alternative to acid wash?

[framcus]

A large number of white stains have accumulated on the bottom of our pool over its nearly 20 year life span. Since the plaster is dark blue these are rather unsightly.

I assume the stains are due to numerous bags of calcium hypochlorite having been sprinkled around the edge of the pool over the years and further calcium deposition due to periodic high pH following poorly controlled pool chemistry. For the last year at least I have predominantly used liquid bleach and controlled the water chemistry myself, so I hope they will not get any worse.

Three years ago the pool was acid washed. Since the pool is large (approx 30,000 gallons), the acid process was a major job and the sight of clouds of hydrogen chloride gas wafting across my yard was somewhat disconcerting. Also the job was not a great success because while some of the more unsightly stains were removed many still remained. I had not seen an acid wash performed before, so I can’t tell whether this was just an unprofessional job or the stains were particularly stubborn or acid wash was the wrong approach, but it seemed a like a lot of risk for a small return. Also emptying and refilling the pool is a major hassle (flood running down hill in neighbor’s yard during emptying and several days of refilling from well with lots of metal in water). Of course there are ways of mitigating these issues (fill from tanker etc), but I would prefer a less drastic approach if possible, even if it takes all summer.

Any suggestions on how to identify the stains, determine what is the best way to remove them and whther it is possible to do this without draining the pool?

Thanks

[mbar]

I'm sorry, but I don't know of any other way to remove calcium build up from gunite pools. I have never watched an acid wash, so I can't comment on what was right or wrong about how they did yours, hopefully someone who has had it done on their pool will chime in. It would seem to me that they would have been able to get all the stains off if it were done correctly. Anyone out there who can help????

[mas985]

Sandpaper will take off some of it but at the bottom of the pool it could take a very long time to do. You could try to get a long pole with wet paper attachment.

[framcus]

I drained a small (1000 gallon) kiddie pool adjacent to the main pool to remove some iron stains and took the opportunity to examine the light colored stains in smaller pool. While there were a few small scale marks (easily removable by diluted muriatic acid) the more numerous light colored stains appeared, on close inspection, to be slight indentations where the lighter colored underlying concrete was showing through the darker plaster. I presume this would be the same pattern for the larger pool if I chose to empty it.

My assumption is that the acid wash performed 3 years ago actually removed not only the scale marks but also the underlying plaster. Does this seem a plausible explanation? It is hard to know whether this was a botched job or an over vigorous wash on an ageing pool surface. Unfortunately it seems likely I will need to get the pool re-plastered if I am to get any improvements on my present situation. Any thoughts?

On a practical note I have discovered that if I turn all the return nozzles to face upwards the rippled water surface hides the discolorations at the bottom of the pool.

[mbar]

I'm sorry, but I don't know alot about the plaster in the pools. Hopefully someone who has gone through an acid wash and is more familiar with the process will be able to help. Personally, I think the return jets rippling on the water sounds like a really good idea:) However, since you recently had it acid washed , I would look into what may have happened so that you know in case you do replaster the pool in the future.