Small pool chlorine consumption rates & levels

[nate]

Helping out the sister with her small pool... (based in Aus)
It used to be one of those "magic mineral" pools when built, then changed to Salt chlorinator, now chlorine & acid dosing... with the magic ORP system. (FFS!)
As "they couldnt get it working right after it was built"... *sigh*

Its a concrete (plaster) pool about 20,000L - a small rectangle 4.2x2.2x1.4m deep, some sunlight (not much) & they keep it pretty clean. 2 kids & use it most days. Temp is currently really high - high 20's low 30's.
Local pool guy said its not uncommon to go through a container of chlorine in 2 days!!! (container = 15L @ 125g/L sodium hypochlorite)
15L in 2 days sounds pretty high - but i've never had a chlorine dosing pool, so not too sure - but used that to shock a larger pool!

He also said to start adding granulated chlorine (calcium hypo) - which given the calcium levels below would be further insanity.
They're also *really* anti-pool covers, they say never to use them as they screw with the chemicals & levels.... (*profanity*)


Current Levels (Taylor test kit)
Chlorine: 1ppm
Total Alk: 25
CYA: zero
Calcium: 525
PH was insanely low, required 11 drops of base reagent

My plan is to add 400ml chlorine to get it up to a reasonable level, add in 1kg of CYA Stabilizer, add 1kg sodium bicarbonate (TA).
That'll get the Chlorine up & stabilizer sorted, the TA sorted, and possibly bring the pH up a bit.
Give it a week, retest & then maybe add 800g sodium carbonate to further bring up the pH if needed.

Thoughts?

 

[mknauss]

That pH must be really uncomfortable to swim in. But as it is fiberglass and does not sound like there is heater, not really harming anything.
Your plan sounds solid. With no CYA the pool would be consuming FC quickly. FC has a half life of just under an hour with no CYA and full sun on the pool surface.

 

[mgtfp]

Local pool guy said its not uncommon to go through a container of chlorine in 2 days!!! (container = 15L @ 125g/L sodium hypochlorite)
15L in 2 days sounds pretty high - but i've never had a chlorine dosing pool, so not too sure - but used that to shock a larger pool!

That does sound insane. If my maths is right, that should be enough chlorine to raise FC by about 95ppm. If that pool guy considers that to be not uncommon to go through in 2 days, than there is something wrong with this guy's understanding of pool chemistry. That's nearly 50ppm per day - 2-4ppm might be acceptable, I am more between 1 and 2ppm.

 

[nate]

@mknauss its a concrete pool, not fiberglass.... and there is a black plastic roof job, it is possibly running through that permanently i think... (sister is getting up to speed on operating it), i'll work that out too.

@mgtfp yep - thats sounds like a ballpark figure, even if you're out by 50% its still silly numbers!

 

[mknauss]

If the pH is below 7, the first order of business is to raise that.