pH/Alkalinity question

[glintontx]

So here are my water parameters:

TA 100
pH 7.8
FC 9
CYA 80

Just last week, I put in muriatic acid to lower the pH to 7.4 but a week later it is back up to 7.8. My TA is right where it should be so I am very confused. I am adding generic bleach from the grocery store...could it be that the bleach is raising the pH? I have read on other posts here that liquid bleach probably won't raise the pH that much.

Any advice??

 

[jblizzle]

Who says your TA should be at 100ppm? Generally we recommend it be lower than that.

How old is your plaster? New plaster can cause the pH to rise for up to a year.
If you have an aeration, that will also drive the pH up.
And the higher TA will make the pH rise faster too.
Also if your top off water has high TA and pH, that will drive it up as well.

 

[glintontx]

Thanks Jason. What do you recommend my TA to be? The test kit says 100-120 for chlorine pools. My plaster is 30 years old...getting it replaced this winter. And yes, I definitely need to check the top off (city water). Good call.

 

[tim5055]

Thanks Jason. What do you recommend my TA to be? The test kit says 100-120 for chlorine pools. My plaster is 30 years old...getting it replaced this winter. And yes, I definitely need to check the top off (city water). Good call.

What test kit?

Check this out: Pool School - Recommended Levels

 

[glintontx]

Thanks. The link says 70-90+ which mine is not too far from. Should i reduce it to 70? My test kit is the TFT-100 from TFTestKits. The laminated sheet that comes with the test says "100-120 for manually chlorinated pools."

 

[jblizzle]

Just lower the TA until they pH stabilizes. Although once you get new plaster, it is going to rise faster.