CH question/mystery

Aug 24, 2016
21
Las Vegas, NV
#1
I have been following TFP since last August. Took control of my pool and couldn't be happier. Thanks to all here that contribute your knowledge and experience.

So this spring I decided to drain and refill my pool due to the sky-high CYA built up by the pool guy over the years. At that time I also learned that the fill water here in LV is about 300-350 CH. So here's the question.....

I tested my brother's pool with Taylor K-2006 the other night. He converted to SWG recently. His numbers are below:

FC:3
CC:0
Ph:7.6
TA:140
CYA:40
CH:125

Since I expected the CH to be a minimum of 350 (he hasn't drained pool and has owned the home for 18 months) I used the 10ml sample size to conserve reagent. I was shocked when the BLUE endpoint was reached with the 5th drop. Unlike with my pool, it did not proceed through a purple-like color for a few drops (blue with tiny red flakes) on the way to blue. It was clear BLUE with 5 drops of R-0012. We both scratched our heads but then attributed the low CH to the recent salt conversion (with water softening in mind). After reading some more here and also getting a better understanding of the ion exchange that takes place in the softener, I am now stumped as to the very low CH reading as the salt should not have lowered CH (at least from what I think I understand).

Educate me! How can his pool test 125 CH with fill water of 300-350 and insane evaporation here in LV. My pool tested about 1000 CH before the drain I performed a few weeks ago (and that was 3 years after previous drain).
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,304
NW Ohio
#2
Ask him if the previous owners ever mentioned a reverse osmosis treatment. This would have removed most CYA and CH and might have been done if they were getting some scaling. That or fill water being trucked in from a lower CH source are the only ways it is likely to happen without rain.

What kind of pool does he have? Vinyl liner?
 
OP
OP
T
Aug 24, 2016
21
Las Vegas, NV
#3
What kind of pool does he have? Vinyl liner?
It's plaster. There is one other thing I recall in his pool history from last fall. He was using some clarifier and pool was quite cloudy. I went over to see what was going on. The filter was apparently completely jammed up. We removed the one cartridge and cleaned off thoroughly. Water flow returned and pressure dropped. We watched pressure closely and it was 25% higher in just 30 minutes. Cleaned filter again. Repeated this several times until pressure no longer increased over 25%. Come to find out, he had thought more clarifier = better and put in WAY more than the recommended amount and continued adding when pool didn't clear.

Is it possible that all of this clarifier caused calcium to precipitate and get filtered out??
 
OP
OP
T
Aug 24, 2016
21
Las Vegas, NV
#5
He does have a water softener although I can't imagine it softens the fill water. I will be checking though. :) I'll take a feel of the walls as well.

One more thing worth mentioning maybe....he has the water heated to 88. Any impact to testing? New heater too, installed over the winter.
 
OP
OP
T
Aug 24, 2016
21
Las Vegas, NV
#7
Re: CH question/mystery [solved]

I suspect the fill water. Test it for CH.
And I suspect you are correct. Mystery solved. Tested the fill water and it is 0 CH. It comes from the softener. Go figure!

This may deserve a separate thread but can you advise why a plaster pool on SWG is recommended to have a little higher CH than one without SWG? Thanks much as always!
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,330
San Dimas, CA (LA County)
#8
Re: CH question/mystery [solved]

And I suspect you are correct. Mystery solved. Tested the fill water and it is 0 CH. It comes from the softener. Go figure!

This may deserve a separate thread but can you advise why a plaster pool on SWG is recommended to have a little higher CH than one without SWG? Thanks much as always!
It's to counteract the corrosive effect of the salt and the higher CYA. Go plug some numbers into poolmath. First column bleach, second column SWG. All things the same in each column but raise CYA and CH to SWG levels and 3000 salt. Then look at the CSI in each case. Go up and down with the values and see what happens. See what happens with temperature. It's pretty enlightening to see how little CH really affects CSI.
 
OP
OP
T
Aug 24, 2016
21
Las Vegas, NV
#9
It looks like as long as he is keeping it like bath water at 88+ degrees then the CSI is fine with the lower CH around 150. No other concern with keeping CH low on the SWG?