tough cloudy water problem

[shooter]

Trying to figure this one out....after addition of HTH, the water turns cloudy white...once muriatic acid is added (~8-10L in a 210,000 L pool), the water turns clear and a brownish precipitate forms at the bottom of the pool.

The original source of the water is a well which likely contains iron. My thought is that the iron is reacting with the calcium hypochlorite to create the original white precipitate that causes the cloudiness, and then clearly the HCl (muriatic acid) causes the iron to precipitate out as iron oxide.

Anyone have any thoughts? I'd like to avoid the initial cloudiness if possible....thinking of trying to use sodium hypochlorite instead of the HTH (which is calcium hypochlorite).

[Guest]

use bleach! It's the same as liquid chlorine and MUCH cheaper!! 1qt per 1000 gallons.

[me]

Trying to figure this one out....after addition of HTH, the water turns cloudy white...once muriatic acid is added (~8-10L in a 210,000 L pool), the water turns clear and a brownish precipitate forms at the bottom of the pool.

The original source of the water is a well which likely contains iron. My thought is that the iron is reacting with the calcium hypochlorite to create the original white precipitate that causes the cloudiness, and then clearly the HCl (muriatic acid) causes the iron to precipitate out as iron oxide.

Anyone have any thoughts? I'd like to avoid the initial cloudiness if possible....thinking of trying to use sodium hypochlorite instead of the HTH (which is calcium hypochlorite).

The initial cloudiness is rather the calcium component from the HTH (calcium hypochlorite) precipitating out of solution. Addition of acid lowers the pH, shifting the alkalinity components in favour of CO2 as opposed to bicarbonates thus bringing the calcium back in solution. I think the cal hypo may be oxidizing the iron, a bit like it when high levels of chlorine react with copper producing lovely black copper oxide. The opposite is true, increasing the pH to 9.5-10 causes the bicarbonate component of alkalinity to prevail and precipitate out the calcium. A neat way to lower calcium hardness if you're up to it

The pool store (oh no!) should have chelating products to keep the iron in solution.

The initial cloudiness caused by HTH should not persist more than a few minutes. Sodium hypochlorite is good for shock too, the required amount is of course not the same compared to HTH, and some people prefer handling a powder than a liquid.