why does ph go back up?

[SerbianPoolGuy]

last night i had

ta 270
fc 1.2
ph 8.7
cya 10

i poured in 2 liters of acid

at 9am ph was 8.2
at noon 8.5
and at 8pm 8.7

why is this happening?

 

[jblizzle]

Please put your pool and equipment details in your signature .. I can not remember you setup.

pH goes up due to high TA and aeration (water features, spa, SWG, etc).

 

[SerbianPoolGuy]

i have a 15000 gallon pool which is 56000 liters
sand filter.. 17000liter per hour pump.. all my gear is made in spain..
i have two skimmers and a main drain..6 returns on the bottom

no water effects or anything hooked up yet..

 

[jblizzle]

So the pH rise is likely due to your high TA. Follow the Lowering Total Alkalinity article in Pool School.

However, you should only start doing that when all other parameters are in range and your pool is clear (I can not remember the goings on in your other threads ... another reason to keep them together).

Your CYA seems too low (not sure how you measured below 20ppm) and your FC is certainly too low. What does your water look like?

 

[SerbianPoolGuy]

the water is sparkling clear
i lowered ph then shocked to 10 using dichlor.. but all day fc was going down and ph going up

 

[jblizzle]

Your FC is dropping in the day time because your CYA is too low ... the dichlor is adding the CYA, so make sure you do not end up using too much and raising the CYA too high.

 

[SerbianPoolGuy]

i was told to get ph to the right level before shocking .. so now i need to lower ta and ph.. after the levels are ok only then should i add dichlor to bring cya up and fc?

 

[jblizzle]

You need to keep adding chlorine (whether you use dichlor or preferably liquid ... the dichlor is helping the CYA situation , but not a long term solution).

You are correct that you need to adjust the pH first ... clearly 2 L was not nearly enough to get you in the low 7s. Keep adding acid and testing after an hour or so until it stays in the low 7s. Doing this is going to automatically lower the TA some.

 

[SerbianPoolGuy]

i added 3l of 16% acid 1h ago

since our new house isnt done yet we dont live there so i can only measure ph in the am

after i add acid .. if i read it right you said i can measure ph levels after 1h?

 

[jblizzle]

It takes no more than an hour for most chemicals to mix through the water with the pump on.

That acid is pretty weak. According to poolcalculator, to drop from 8.7 to 7.2 would require almost 7L (of course adding that much at once is not a good idea). I would guess you will need at least another 3L if you test again after an hour.

 

[SerbianPoolGuy]

ok ill try again tomorrow.. cant source stronger than 16% :-(
thx for the help. appreciate it

 

[SerbianPoolGuy]

Ph went down only to 8.5 even though i added 3l of 16% acid.
Any idea whats going on?

 

[anonapersona]

Are you testing pH while FC is above 10? pH test is not reliable at FC above 10.

Also, if you use dichlor to shock you are increasing the CYA and must calculate the new CYA after that addition to determine the new shock level for the new CYA level. It is easier to use a chlorine source that does not include CYA if you can find it.

 

[Richard320]

Are you testing pH while FC is above 10? pH test is not reliable at FC above 10.

Also, if you use dichlor to shock you are increasing the CYA and must calculate the new CYA after that addition to determine the new shock level for the new CYA level. It is easier to use a chlorine source that does not include CYA if you can find it.

You must not be paying attention to his other threads. Plain CYA is apparently unknown in Serbia. Dichlor is the best choice for him.

 

[jblizzle]

most of tests here max out around 8.2 or so. And the test shows that even if it is higher, so likely your pH is just very high and the high TA makes changing it difficult.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[UnderWaterVanya]

I'm betting the acid is weaker than spec says. Is dry acid available there?

 

[SerbianPoolGuy]

Ph at 7.4!!! Took twice the dosage of acid leading me to believe the acid is weaker than stated as vanya suspected...

Also picked up a dtd tablet tester and its more accurate than aqvacheck.. btw aqvacheck digital sucks it always shpws different values

 

[UnderWaterVanya]

Ph at 7.4!!! Took twice the dosage of acid leading me to believe the acid is weaker than stated as vanya suspected...

Also picked up a dtd tablet tester and its more accurate than aqvacheck.. btw aqvacheck digital sucks it always shpws different values

All the digital color matching methods seem to have problems with repeatability. I'd rather have a test that gives the same result over and over when done in the same way than one that doesn't any day! LOL

Your pool is fantastic and I'm crossing my fingers that you have a trouble free pool.

 

[SerbianPoolGuy]

I just read that high TA could be caused by a pool being new, (plaster pool) my pool is made of concrete, and it has mosaic tiles and in between is filled with... plaster? (not sure how u say it in english) could this cause the high TA?

If yes, then what do i do?

 

[jblizzle]

how new is the tile?

The solution is just to keep adding acid to lower the pH to start in range which will also lower the TA. See the article in Pool School about lowering TA.

Posted from my Droid with Tapatalk ... sorry if my response is short