CH rising... and rising... and rising...

[tfoggo]

My CH seems to be getting out of control! Does this matter (CSI remains 'Balanced' according to PoolMath)? What might be causing it? TDS is also inexorably rising.

I note that the recommended CH level is 0-350, and my air-source heat pump instructions recommend I keep it at 250 or less.

I stopped using dry Cal Hypo (unstabilized) in January this year and switched to liquid Sodium Hypo (14/15%). At that point my CH was 410.

Today (roughly 6 months later) my numbers are:

FC: 8.20 (drifting down after a SLAM: target = 5)
CC: 0.4
TA: 50
pH: 7.2
CH: 840 (so that's more than doubled in 6 months!)
CYA: 30
CSI:
TDS: 1,920

CH of source water is 300.

Water is crystal clear.

Any advice much appreciated!

All the best.

 

[pooldv]

First, yes, as long as the CSI is +0.6 or lower there is nothing to worry about with calcium scale forming. That is also the reason the heater recommends lower CH, to help prevent scale forming in the heat exchanger.

It is difficult to explain how CH could rise that much unless there was calcium scale present and lowered pH dissolved the calcium back into solution. Or there are errors in the test results.

More here, Pool School - Calcium Scaling

 

[tim5055]

My thought would be your testing. I see you are using a Palintest Pooltest 9 Premier photometer. While we don't see that particular unit on this side of the pond, we do see a lot of ColorQ 7. We have had members attempt to use the ColorQ to follow our methods and almost all have abandoned its use due to inaccuracies and inconsistencies. We even had one member test the same sample of water three times in a row and ended up with three different sets of results. Here is an example of a ColorQ post: ColorQ vs TF100 and here is a review where the Color Q was used alongside a TF-100. Test Kit Comparison

You may want ot see if you can find a drop based test to verify your testing. Some thing like a LaMotte 7022 which I think is available in your area.

 

[tfoggo]

Many thanks pooldv, very helpful.

So am I right in thinking that my CH level is largely irrelevant as long my CSI remains close to zero?

 

[Jezza]

The short answer is yes for a vinyl pool.

 

[tfoggo]

Thanks all for your advice. I'll mothball the photometer for now and see how I get on with the LaMotte 7022 drop test kit which, funnily enough, I bought just this week.

All the best.