How much to worry about CSI after pool wtr reverse osmosis?

[MattM]

Calcium in our pool reached our high threshold point earlier this month and we had reverse osmosis service performed to bring it down. And, yes, it brought nearly everything else down as well.

PH dropped to 6.8, TA dropped from 120->50, Borates went to almost zero, salt to 800, CYA to under 10, calcium to slightly under 100. Luckily, I had planned ahead and had replacement supplies on hand.

The RO service took about 17hrs and afterwards our CSI was briefly about -1.6. I got the borates in rather quickly to raise TA and PH, and then brought down CSI back into the -0.35 to -0.50 range over about 36hrs. Salt is back to 3400 and all appears to be running fine. The pool has stayed in the low CSI range for the last week - I was hoping warmer weather would help get it back above -0.30 but it may take another week or two to know if we get sustained higher temps. Due to our intellichem, the highest sustained PH I can keep is ~7.65.

Should I just wait or add a small amount of calcium to the pool water now, or how long can I reasonably wait with CSI this low? We have a pebble sheen finish that we try to be careful of. CH is currently 125 and I can see bringing it up to 150-160. Normally, CH increases by 10 pts during each winter month, and 15-30 pts during summer months.

 

[JasonLion]

Re: How much to worry about CSI after pool wtr reverse osmos

CSI at -1.6 is only alright for very short periods. CSI at -0.5 is fine for quite some time, if not forever.

 

[Richard320]

Re: How much to worry about CSI after pool wtr reverse osmos

You're in the safe zone, so don't worry.

Also, do not freak out if CH climbs a little even if you haven't added any water. If you have any scaly patches, they may start dissolving, which will raise CH. It doesn't mean it's leeching it out of the plaster.

 

[MattM]

Re: How much to worry about CSI after pool wtr reverse osmos

K, I had been keeping CSI in a tight zone between 0 and -0.2 ever since the pool was first started up...glad to hear that -0.5 should be safe enough until the water temp increases. That is a lot of stress off my shoulders.

In any case, I wouldn't think that I'd have any scale to dissolve given that the csi had always been kept slightly negative....but there was the jump from 100 to 125 during the last week, but hopefully it is holding steady now.