pH, 7.4 or 7.5?

[Malico]

I have a Sense and Dispense using MA. In theory (it is problematic at the moment) once i get this thing dialed in it should be able to maintain the pools pH to the set level. My question being, do I set 7.4 or 7.5? Or am I overthinking this which is entirely possible?

Edit - My reason for 7.4 over 7.5 is that it is in the middle of 7.2-7.6, allowing some error buffer room on the sensor and my own testing.

 

[woodyp]

You're good either way.

 

[Oly]

No difference, just monitor your water to keep it in the zone.

 

[Poolzzz]

It's a 1% difference. I highly doubt the measurements are that accurate!

 

[jblizzle]

I think you may find you use a lot more acid trying to keep the pH that low. The pH you want to maintain is largely dependant on the rest of your pool's chemistry levels.

It might be much more stable up around 7.8. Although with a SWG, you want to keep the CSI at or just < 0.

Do you have a full set of test results?

 

[Malico]

These are my results as of last night

Temp - 82
FC - 3.5
TC - 4
CC - <0.5
pH - 7.1
TA - 130
CH - 250
CYA - 40
Salt - 3200 with test strip, 3200 average showing on SWCG
SI per the Taylor wheel - -0.28

I did check FC and pH this morning, 5 and 7.3 respectively. Still actively aerating plus adding CYA via a sock.

When I use the wheel and put my pH to the target of 7.4-7.5 it puts my SI at roughly -0.08. I think I can be pretty happy with that.

I just ordered by T-100 kit, so hoping to have my FC/TC levels a little more accurate.

 

[jblizzle]

Forget the wheel. Use PoolMath.
I just put your numbers into PoolMath and it gives a CSI of -0.5
You may be looking a LSI?

All things left the same, a pH of 7.6 would put you right at a CSI of 0. (Well, -0.07 when your CYA gets up to 80ppm)
As your TA goes down, you may be able to keep the pH a little higher and greatly lower the amount of acid needed to keep it there.

 

[Malico]

Will do, thanks for the help!