Adjusted my mash PH from filtered water, 1 day later the PH went up

[beervoid]

Hello everyone,

I've got filtered water in my house and measured a PH of 6.60

I've added drops of phosphoric as a test to see how much it would lower per drop.
I shake the bottle after adding a drop and measure again.

After 10 drops my PH was down to 5.50
I've let the bottle sit for one night and measured again my PH and now it's back up to 6.0

I've tested my cheap PH meter in a 4.01 solution and it was correct.
I've also also tested it in water with baking soda which gave me 7.9 PH so it seems my meter is still alright.

I've got a few questions.
- Is the water plus baking soda method fool proof? It should work with any water source and no need for exact amount of baking soda.

- is it possible for water PH to go up?

- if I know how many drops of phosphoric acid are needed to bring down the PH of 6 liters of water does that mean I can calculate double the amount of drops on 12 liters of water?

Cheers!

 

[thehaze]

I have no idea if the pH of the water can rise from day to day.

Drops are kinda hard to figure out, but maybe try to use like a little seringe, and use 0.5-1 ml measurements, which are probably easier to account for and note down.

pH meters should be calibrated every time you sue them and they usually have two points of calibration: 4 and 7. This will probably be better to get an exact measurement, but it depends from one pH meter to another.

Do you know if your filter also filters out minerals? It would be good to know what your water contains.

 

[beervoid]

I have no idea if the pH of the water can rise from day to day.

Drops are kinda hard to figure out, but maybe try to use like a little seringe, and use 0.5-1 ml measurements, which are probably easier to account for and note down.

pH meters should be calibrated every time you sue them and they usually have two points of calibration: 4 and 7. This will probably be better to get an exact measurement, but it depends from one pH meter to another.

Do you know if your filter also filters out minerals? It would be good to know what your water contains.

It's not an RO filter, it's a 5 stage filter with carbon filter and others... I don't think all minerals are filtered out so I'm suspecting the buffering effect of minerals in the water could have been the culprit of raising my PH over night?

I will be testing this out on RO water as well just to see what happens.
I'm figuring that 1 drop should always be the same measurement, im using an eye dropper... Will give syringes a try as well

 

[ajdelange]

I've got filtered water in my house and measured a PH of 6.60

OK

I've added drops of phosphoric as a test to see how much it would lower per drop.
I shake the bottle after adding a drop and measure again.

After 10 drops my PH was down to 5.50
I've let the bottle sit for one night and measured again my PH and now it's back up to 6.0
It's not an RO filter, it's a 5 stage filter with carbon filter and others... I don't think all minerals are filtered out so I'm suspecting the buffering effect of minerals in the water could have been the culprit of raising my PH over night?

It's hard to imagine a 5 stage system that is NOT an RO system but we have to assume you know what you have or don't have. The fact that the water drops only 1.1 suggests that the water is quite alkaline. This would be the case even were the phosphoric acid 10%. We really can't tell you much without knowing what the strength of the phosphoric acid is and the volume of the water you added it to. It would also help to know what those "other" 4 stages of filtration are.

I've tested my cheap PH meter in a 4.01 solution and it was correct.
I've also also tested it in water with baking soda which gave me 7.9 PH so it seems my meter is still alright.

To verify that your meter is OK you need to use two buffers. Baking soda in water is a terrible buffer unless you adjust it's pH to near 6.38. In pure (low mineral water) you should read pH 8.4 or so for a bicarbonate solution but as I said it has very little buffering. "Cheap" when applied to pH meters is always a red flag. Sometimes they work and sometimes they don't.

I've got a few questions.
- Is the water plus baking soda method fool proof? It should work with any water source and no need for exact amount of baking soda.

No. As bicarbonate has little buffering right out of the package it is easily pulled away from its intrinsic pH. Note that the 10 buffer we use to calibrate pH meters is a bicarbonate buffer but it is tuned to be within 0.38 of carbonic acid's second pK. You will need the 4.01 and 7.00 NIST traceable buffers to verify your meter's performance. There is a Sticky in this forum that tells you how to do that.

- is it possible for water PH to go up?

Under some circumstances, yes. It is more likely here, however, that your meter drifted.

- if I know how many drops of phosphoric acid are needed to bring down the PH of 6 liters of water does that mean I can calculate double the amount of drops on 12 liters of water?

Yep.

Will give syringes a try as well

Good idea.