What causes are there for PH to drop in hot tub

[teach]

I have never really had muchof a  problem with keeping my tub water balanced, but recently over the past month I have noticed that the Ph always seems to be much lower than it usually is....having to add PH increaser alot on a weekly basis.   What causes PH to drop?  

[Chad]

Are you using an unbuffered mps and what is your TA?
What is your primary sanitizer?
Sorry for all the q's.

[DrOperations]

I, too, have the similar experience.  I use Leisure Time's Renew MPS.  I don't know if it is buffered or not.  Anyone know?

[Chad]

I, too, have the similar experience.  I use Leisure Time's Renew MPS.  I don't know if it is buffered or not.  Anyone know?

It's buffered.

[teach]

I use oxyspa,100% pure DuPont® Monopersulfate Compound (spa activatior) which is a MPS ,I order from Spa Depot on the internet, I believe it is buffered, as my primary sanitizer.  My tub uses a Silver Iodine cartridge inside spa filter and Ozone. Once a week I use 3 oz of activator as a shock and sometimes ocassionally substitute Sodium Dichlor instead of the activator as the shock.  Water is usually always very clear, but the PH seems  to be very low each week I test it.   I know I could do a water change, but its freezing cold here and would like to put that off till warmer weather.  Just wondering about the low PH?
                      Thanks  

[Chad]

I use oxyspa,100% pure DuPont® Monopersulfate Compound (spa activatior) which is a MPS ,I order from Spa Depot on the internet, I believe it is buffered, as my primary sanitizer.  My tub uses a Silver Iodine cartridge inside spa filter and Ozone. Once a week I use 3 oz of activator as a shock and sometimes ocassionally substitute Sodium Dichlor instead of the activator as the shock.  Water is usually always very clear, but the PH seems  to be very low each week I test it.   I know I could do a water change, but its freezing cold here and would like to put that off till warmer weather.  Just wondering about the low PH?
                      Thanks  

The Oxyspa mps is definetly not buffered, has no sanitizing capabilities, and is the cause for your constant addition of alk/ph increaser. Mps is purely an oxidizer. The only primary sanitizers I know of are chlorine and bromine, all other things like ozone and  mineral catridges should only be used as a secondary sanitizer in conjuction w/ chl or br.
Would I be correct in saying that some weeks there is no addition of chlorine to your water?
How long have you been using your current system/routine?

Thanks

[Steve]

Always adjust Alkalinity before pH. There's no use attempting to raise pH if your alk is low.

Steve