Cleaning Stains

[AllanB]

A friend of mine has asked me to clean the area around his pool, which is finished in fairly porous non slip clay tiles. The pool is fiberglass and has a salt water chlorinator and because the pool is quite full and flush with the surrounding area,, it overflows and regularly floods the pool surround tiles, especially when the kids are doing their thing.

Two years on, the surround tiles are now very badly stained, with brown streaks. Yesterday we tried bleach, with a very limited effect, we left them to soak but without much difference.

Anyone have any ideas what the stains would be and how to remove them? There is another problem the around the tiled ares are flower beds, so we must be careful not the damage them.

[SantiSuk]

Very unlikely you would clean stains form a porous medium - the stains are likely to be deep seated.

You could do a test using hydrochloric acid diluted and left on. 100% hydrochloric would be very difficult and dangerous to use (full safety gear job, but in fact a good mask, goggles, chemical gloves, wellington boots etc is needed whenever you handle HCL at high concentrations (over 25%). Of course you would need to consider the implications for the pool if the wash off is going to migrate pool-wards; thats probably easier to deal with than if the pool side run off water migrates towards the flower beds though.

Start by testing at a low concentration. The domestic cleaner Vixol plus (available in my local town Tesco Lotus, so presumably widely available in supermakets) is 20% HCL; probably only needs heavy duty domestic gloves to handle (I don't read Thai - in a well ventilated outdoors area I would wear the gloves and a face mask). Use one out of the way tile as a test area. Work your way up the dilutions if that doesn't work.

I'm pretty sure 100% HCL would bleach the tiles, but it might be difficult to get an even finish effect. If you are working with higher levels of HCL it is a good idea to wait for a day with a light to medium breeze to take the fumes away from you pronto.

I am no expert on this except that I do a lot of cleaning around my house using a variety of cleaners and I use 100% HCL in the pool (very carefully!). I have noticed its bleaching effect at that concentration when the spill back from the plastic container leaks onto the concrete path beside my pool room.

I would hesitate to use anything above domestic cleaner concentrations of HCL unless you have used HCL before.

100% HCL is avaialable in 25kg containers at 255 baht in the largest/best stocked of the Watsadus in my regional capital (Ubon) but most watsadus don't stock it so you might need a pool shop.

Sorry if the paranoia is wasted on you as you are an experienced chemical user (quite likely if you are a pool man and I seem to remember something about you being a chemical engineer or some such), but this is a public forum and any reader should be aware that HCL is bluddy dangerous stuff.

[AllanB]

I think you have me confused with someone else, I am neither a pool man, nor a chemical engineer and don't think your rhetoric is at all paranoiac just sensible.

I have worked out that they are iron stains from the ore in the water supply, we were slightly successful, with vinegar and detergent and a steel pan scrub, but it was very hard work, since as you said the stains were deeply ingrained.

I didn't want to go stronger than vinegar, stains are one thing surface damage another and he is trying to sell the house, so I guess no easy answer to this one..

[Chaichara]

Try Staintrine™. Ask for it in pool shops or search for it online. Comes in 1 quart and 1 gallon bottles.