Increased Acid Demand

[Phillbo]

Not a major issue but more of a curiosity. I typically add a quart of MA once a week to keep my pH at about 7.6. The last month or so it's been needing a quart twice a week. pH will spike up to 8.0 every 3 days or so.

TC 4
CC 0
Ph 7.6 (added acid last night)
TA 100
CYA 50
Salt 4300

The only change I've made recently was increasing my salt level. I over did it and went higher than I wanted. Was shooting for 3800 but went to 4300 due to a mistake while testing. Could the increased salt level be responsible for increased MA demand?

[waterbear]

Have temperatures been higher lately? Higher temp=faster outgassing of CO2.
Also, it is often necessary to increase cell output, pump run time, or both when the temps are higher to maintain FC at the desired level. Either or both of these actions translate into higher acid demand.

Ecomatic recomends a CYA range of 50-80 ppm. By raising your CYA to 80 ppm you should be able to lower your output percentage and that will translate into lower acid demand. It is always best to run the CYA at the SWG manufacturer's recommended max in an outdoor pool.
Also dropping your TA to 70 will lower acid demand because there will be less outgassing of CO2.

Finally, if you add borates to 50 ppm it has a few effects:
1. the algaestatic properties often lower chlorine demand allowing you to lower the output percentage further, which will translate into lower acid demand
2. the secondary borate buffer system tends to move pH downward as opposed to the bicarbonate buffer (TA) that moves pH toward 8.2.
pH tends to "lock around 7.7 for a longer period of time than without borates before rising above 7.8.

Increased salt translates into increased conductivity in the water. This could cause higher generation of hydrogen gas and more outgassing of CO2 as a result but I think that temperature is the most likely culprit.

[Phillbo]

It's summer time in Az, It's HOT ;)

I'll up the CYA, lower the TA and add some Borates.

Thanks for the input !!

[waterbear]

This post (http://www.poolforum.com/pf2/showpost.php?p=64309&postcount=22) might help you with the borates and some other SWG water balance tips.