PoolMath suggests half the required HCl

[GeoQuack]

PoolMath has worked well for me for all adjustments other than pH. I find that I need about double the suggested HCl to lower the pH by a certain amount than what PoolMath suggests.

My chemistry is as follows:

FC 6
CC 0
pH 7.6
TA 70
CH 410
CYA 80
Na 4400
Temp 18 degrees C

My only idea is that there is a buffer in the pool that I am not aware of. I have not added borates to the pool, and I doubt the previous owner would have. Do you have any alternative explanations or suggestions of the buffer?

 

[JoyfulNoise]

Are you sure your MA is 31.45% (20 Baume)? Many places sell pool acid as well as contractor MA that's 15% because it does not fume.

 

[GeoQuack]

Are you sure your MA is 31.45% (20 Baume)? Many places sell pool acid as well as contractor MA that's 15% because it does not fume.

Yes, it is 32%. It certainly does fume.

 

[smackdab]

Some types of Dichlor shock contain borates as an additive. Not sure what kind is available in Australia but maybe they used that. Try a borate test.

 

[GeoQuack]

Will try a borate test, just have to find a shop that sells them.

 

[AUSpool]

Will try a borate test, just have to find a shop that sells them.

Don't bother looking in the shops, online is your best bet.

Our acid is is definatly full strength. I've never aclually tested my pH after the recommended PoolMath dose but I recently had a 50% difference between the acid demand test and PoolMath. You might be on to something.