Magsalt (Magnesium Chloride) turned pool green

[tomfrh]

Our pool was replastered a month ago. I added salt yesterday, plus two bags of MagSalt (magnesium chloride):

Hy-Clor 12.5kg Mag Salt Pool Chemical

Find Hy-Clor 12.5kg Mag Salt Pool Chemical at Bunnings. Visit your local store for the widest range of products.

www.bunnings.com.au

The pool is now green!


Looking at the reviews above, it seems a common issue. Our pool looks like that.

What is the green colour? How do I fix it?

 

[JohnT]

I’d guess it’s either impurities in the salt (likely iron) or some kind of effect of the magnesium added causing iron already in the water to change form.

It’s very common for iron in the water to look green, when actually it stains the water yellow which looks green against the blue pool surface.

 

[Jimrahbe]

Tom,

Why would you add that Pool Store Magic to your pool?

Nothing that it does is necessary for a well maintained saltwater pool.

Who's idea was it? Have you used it before?

Thanks,

Jim R.

 

[tomfrh]

Why would you add that Pool Store Magic to your pool?

I know, I know...

Who's idea was it? Have you used it before?

I'll blame my neighbour.

I've never used it before.

 

[tomfrh]

It’s very common for iron in the water to look green, when actually it stains the water yellow

Ahh, so it's actually yellow combining with the blue water colour. That makes sense.

How to get rid of the iron?

 

[Newdude]

How to get rid of the iron?

There are many threads and just as many DIY contraptions built to catch it. MGuzzy was kind enough to detail his.

What I thought were old iron stains on my cartridge filters, is iron my water!

Hi all Amazingly I found no posts on the forum about this. So I was the victim of the dreaded Iron contaminated Clorox Pool Salt about 3 seasons ago. Apparently it was worse than I thought. There is a nice darker area in my mottled dark plaster in the deep end from salt additions from that...

www.troublefreepool.com

 

[tomfrh]

The green colour has almost gone away after a day of filtering, and the filter cartridge has gone yellow.

Why do people catch it if it filters out? Does it ruin the filter?

 

[zea3]

It doesn't always filter out. Sometimes when you add chlorine it oxidizes the iron and turns the pool brown. Plus you have a cartridge filter and a sand filter would not capture the iron particles. The additional filtration speeds up the process of getting the iron out.

 

[AUSpool]

If you compare the sds’s from a few brands they vary in purity from 95% to 98%. 5% is impurities not disclosed where the better salt brands at $10 a bag are 100% sodium chloride. The sales pitch for this “mineral salts or crystals” promotes the “known” health benefits and likens the product packed it China to the Dead Sea salts. If there are any health benefits to be had, our pools that are topped up with tap water will have some magnesium already in them.

Magnesium is known to interfere with the CH test at elevated levels.

And as an interesting side note when you compare sds data for magnesium and cyanuric acid the toxicity levels are almost identical. Can I deduce from that that if there are health benefits from magnesium then there must be identical benefits from CYA? - Just saying...

 

[tomfrh]

Magnesium is known to interfere with the CH test at elevated levels.

This is my problem now. My calcium tests don’t work. The clear choice labs test doesn’t work anymore, nor do the bunning hardness test strips (which were always a pretty good match for the clear choice test).

What do I do here?

I put 25kg of magnesium chloride into our 50000L pool

 

[AUSpool]

This is my problem now. My calcium tests don’t work. The clear choice labs test doesn’t work anymore, nor do the bunning hardness test strips (which were always a pretty good match for the clear choice test).

What do I do here?

I put 25kg of magnesium chloride into our 50000L pool

There are a couple of tips here in the extended instructions.

 

[JoyfulNoise]

This is my problem now. My calcium tests don’t work. The clear choice labs test doesn’t work anymore, nor do the bunning hardness test strips (which were always a pretty good match for the clear choice test).

What do I do here?

I put 25kg of magnesium chloride into our 50000L pool

That much magnesium chloride will raise your general hardness (magnesium + calcium hardness) by 475ppm. There are general hardness indicators that are similar to the CH test. You could use a test like that and then see how high your general hardness is and subtract the 475ppm pert from the magnesium chloride addition. It's not perfect but it's close enough.

Just so you know, magnesium does precipitate out of solution as magnesium hydroxide when the pH rises above 10.1. That's not typical in the bulk volume of the pool water but a pH like that can be easily attained inside a running SWG cell. So you'll want to pull your SWG and look for a mushy white scale. You should be able to easily spray it off with a strong jet of water or chemically remove it with a diluted acid treatment.