High levels of CH in fill water what to do?

Eniala

New member
Jun 24, 2019
2
UK
I have been lurking for a couple of years but not posted before. The information on here is fantastic, by far the best on the internet. However I have hit a problem that is causing me a nightmare. My 1 year old, partially in-ground, steel walled pool has a huge scale problem. Due to a large building project I haven't had access to the pool for about 6 months so it was not closed properly for winter (or the water tested), it went black, not even green, with lots of algae and mosquito type nymphs growing in it. We decided to change the water rather than add masses of chlorine for a SLAM (we used the water to water a very dry garden as it had no chemicals in it; I've always only used liquid chlorine which had long since disappeared in the murky depths of my pool), however this revealed that we have a solid layer of scale over the entire pool, which seems to have appeared over the winter. It is particularly bad over the entire bottom of the pool. As we have a plain sand coloured liner it shows as horrible brown and green staining but also feels very rough. The only way I've found to get rid of this, is with a power washer (I know it's risky and far from ideal, but we're being careful and it's easier/cheaper than getting a new liner which is basically the position we are in). A brush doesn't touch it and it's too big a problem to use chemicals. We didn't have this problem with our old pool which was an 18ft, 52inch round AGP.

We are going to refill in the next couple of days, but my question really centres around my tap water.

When tested: (using Taylor K2006C)
FC = 0.4
CC = 0.6
PH = 7.2
TA = 210
CH = 350

Is there a way to reduce Calcium Hardness found in my supply water? I had no idea about this until reading TFP this week, I've read the Calcium hardness info on here and the various threads I can find, but most information seems to be about increasing CH in plaster or tiled pools, as low CH is not a problem in liner pools (which would be normal in most water supplies), but what if your supply water has high CH to start with? Will it be enough to reduce TA? At the tap water temp of approx 12degrees centigrade its not a problem, but as soon as it starts heating up it will raise CSI above 0 which I believe will cause scaling. I don't fancy pressure washing the vinyl again, I don't think it, or me for that matter, could take it!

Thanks for any advice.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,209
Tucson, AZ
:wave: Welcome to TFP!!!

With higher CH in your fill water, you will just need to keep a closer eye on your pH which will eventually lower your TA as well.
Having CSI a little above 0 is fine. You just do not want it to get above +0.5

The only way to lower the CH is through a Reverse Osmosis treatment, but I highly doubt you have the services available there that do it, plus it is expensive.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
21,250
Laughlin, NV
Welcome to the forum!
There are a couple ways to reduce CH, one is reverse osmosis, the other is a water softener. Not likely you have either.
But a CH of 350 is not a big deal. You know about CSI, so get your TA lower (say 70 ppm) and keep your pH below 7.8 and you will not get scale. As long as your CSI is normally below 0.3, you should have no issues.
I manage our pool to a CH of nearly 1000 ppm. Others on the forum go higher.
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.
 

Eniala

New member
Jun 24, 2019
2
UK
Thanks very much for your replies. I guess I'll just have to watch TA and PH a bit more closely. We do actually have a water softener installed in the house but the outside tap is plumbed in before that. I'm not sure the softener could cope with filling the entire pool, but maybe topping up in the future could be from a hose attached to a softened supply tap in the house. I hadn't actually thought about that, so it's a good suggestion!

Thanks again.