High CH

[Blivit79]

I am in to year 2 of pool ownership and self maintenance. I have had my fair share of issues along the way but nothing some research here couldn't take care of.

Right now my water looks great and test results confirm this...except for my CH reading. I usually only test this about 1x per week and prior to this it used to hover around 300-350 no matter what. I started testing it more often when I noticed the increases. My test today showed 475. It has been on a gradual rise since about the end of April (4/16 tested at 325.)

Todays tests:

Temp: 84
PH: 7.5
FC: 7.5
CH: 475
TA: 70
CYA: 45

Timeline of some "different" events I had and of the CH readings:

4/9: replaced cartridge filter of unknown age
4/16:CH tests at 325
4/21: pump impeller sheared. System was off for 3 days while a new part was ordered and I installed it
4/29: CH test at 400
5/11: CH 375
5/14: CH 400
5/17: CH 425
5/21: CH 400
5/28: CH 400
6/4: CH 450
6/5: CH 475

Between those dates I added only bleach and muriatic acid as I had always done. I did add some baking soda on 5/14 as my TA had gotten a little low.

So I am a bit confused here. Why would my CH readings be so high after staying around 300-350 for more than a year? Should I be concerned? Everything else is testing fine and the water looks great. Is my testing flawed? If I do need to lower it, is my only choice draining water?

This is central florida so we do get a lot of rain but again my CH was never this high before. I haven't had to lower the water level in a while but could probably use to drop it down about 1 inch.

 

[basod]

There's a few reasons it could rise like that.
Calcium can be released from the surrounding pool decking during rains.
The Gunite could be releasing it naturally or during a pH excursion.
Evaporation and refill. If you haven't lowered the water level in a while it could be evaporation leaving behind the CH
Have you ever tested the CH of your fill water?

 

[Blivit79]

There's a few reasons it could rise like that.
Calcium can be released from the surrounding pool decking during rains.
The Gunite could be releasing it naturally or during a pH excursion.
Evaporation and refill. If you haven't lowered the water level in a while it could be evaporation leaving behind the CH
Have you ever tested the CH of your fill water?

I've never actually had to fill. I've always relied on rain water then drain some out if and when I need to.

 

[duraleigh]

Generally, you can expect CH to rise in most pools, if your fill water has a low CH, it is never an issue.

 

[tstex]

My CH was 450-475, this this was mainly yr one when the plaster was curing/releasing Ca. This year it has gone down due to rains and maturing of plaster. My fill water CH was 125-150.

Question, does your pool have a drain? if it does and it rains a lot, make sure you turn-on the pump and circulate the water so the rain water [least CH] does not just drain off the top...mix it up and get some of that stronger CH out the drain when it rains...

Also, I have 4 deck drains so unless we get another 16" rain, nothing from my deck will get into the pool...well, just spot amt's from skimmer cover plates w small finger holes. That would be almost in consequential.

Also, you should periodically test your fill water...however you test it, do the same way each time.

 

[basod]

Question, does your pool have a drain? if it does and it rains a lot, make sure you turn-on the pump and circulate the water so the rain water [least CH] does not just drain off the top...mix it up and get some of that stronger CH out the drain when it rains...

Also, I have 4 deck drains so unless we get another 16" rain, nothing from my deck will get into the pool...well, just spot amt's from skimmer cover plates w small finger holes. That would be almost in consequential.

Also, you should periodically test your fill water...however you test it, do the same way each time.

^All really sound advice
People don't realize how much CA can leach from concrete surrounding the pool - even worse when fresh, but it constantly dissolves when swimmers are running around

 

[Blivit79]

I think I should have specified, this isn't a new pool but it is a new to me pool. We bought the house early last year, the pool was installed in 1995. I have just noticed the high CH this year which is going into my second year of maintaining.

My pool does have a drain and I do have to use it frequently to keep my water level correct following rains. We have just had some tropical storm bands go through here so the water level is really high again. I haven't tested CH since Sunday but will once I drain some water.

Mainly I just wanted to know if I should be concerned.