Can my chlorine be high while SWCG output is low??

[waterbear]

Just want to double check about putting in dry acid -- I thought there could be lots of problems if I put in more than a certain amount at a time. According to the chart on the dry acid, in order to lower my ph to 7.0, I'd have to add way more than the recommended amount at once to do it in one shot. Any advice? (Again, I have a 25,000 gallon pool).

-- Jody

If you need to lower your pH by a certain amount you need to add enough acid to lower the pH. Period. How much you need will depend in part on the current total alkalinity. If it is high you will need more acid. if it is low you will need less,. The only way to know how much you REALLY need is to use an acid demand test such as found in the Taylor k-2106 test kit. A rule of thumb is that 1 pt per 10k gal will lower the pH by .2 to .6, depending on the TA and whether borates are present. Like i said the only way to REALLY know is with an acid demand test. An alternative is to add a fixed amount WITH PUMP RUNNING, wait an hour, retest pH, and repeat until pH reaches desired goal. Not as exact or as quick but workable.

Dry acid should always be predissolved in a bucket of water (where it forms sulfuric acid, btw).

Also, with a SWCG it is better to use muriatic acid instead of dry acid. Dry acid will add sulphates to your water and these can be damamaging to some salt water cells. Muriatic acid is also less expensive and more effective (less is needed for the same pH drop.)

[Jodester]

Dry acid should always be predissolved in a bucket of water (where it forms sulfuric acid, btw).

Also, with a SWCG it is better to use muriatic acid instead of dry acid. Dry acid will add sulphates to your water and these can be damamaging to some salt water cells. Muriatic acid is also less expensive and more effective (less is needed for the same pH drop.)

I do pre-dissolve the dry acid in water.

I got kind of scared away from muriatic acid after hearing about all the safety precautions in handling and storing it -- not keeping it indoors, even in a shed; keeping the container wrapped in plastic and then also stored in a covered garbage can; the fact that the pool store itself says they don't sell it as indicated by law; wearing a mask when handling. Are my fears founded?

[aylad]

Muriatic acid is something to be respected, but if you are careful with it, as with any other chemical, it's okay. I don't know why the storage in a covered garbage can precaution--as long as you can contain any spills as well as the fumes, then the garbage can is not necessary. I keep mine in the jug it is sold in, with the cap on tightly, inside a WalMart bag, and I keep it in my garage. I have had no problems with storing it that way, whatsoever.

You do need to be careful when you use it--if you spill it on a concrete deck and don't wash it off, you'll find pits in your concrete. However, if it splashes on your hand, it doesn't start to instantly disintegrate, like some would have you believe--all you have to do is stick your hand in the pool and wash it off, and all is well. The real danger when dealing with this stuff, other than getting it in your eyes, is breathing the fumes. They ARE dangerous, and I can tell you from experience that if you get a good whiff of them, it is a very painful experience. When you open the container, the fumes are usually visible--look like smoke-- so as long as you stay upwind of them, then there is no problem. I usually hold my breath while pouring, though, just to be on the safe side. Only takes once.....

Long story short, if you store it with the cap on where it can't spill, and wear gloves and eye protection and stay upwind of the fumes, then it's a perfectly good, efficient chem to use to lower pH (and more cost effective than trying to use dry acid). I just pour it slowly into the return stream from a plastic measuring cup that I have dedicated to pool use, and it works quite well. Thoroughly wash off any spills/splashes, and you'll be fine.

By the way, if you have a Tractor Supply Co store near you, they are the cheapest source for muriatic that we have in this area--a good bit cheaper than Lowe's and Home Depot.

Janet

[waterbear]

What Janet said. Dry acid is not really much safer, btw. Let me make a guess here, you heard about the 'safety precations' from the pool store that does not sell it, right? Think about that. FWIW, I keep mine in a cabinet in the garage sitting in a plastic bucket as a safety precaution against leaks or drips (which, to the best of my knowledge, have yet to happen). The main precaution is not to store it around chlorine products or in an area where kids or pets can get at it.

Also, you might have muriatic acid in your house right now and not even know it. It is an ingredient in many liquid toilet bowl cleaners!