SLAM questions

[dan52]

Backstory: I got the pool mostly cleared up ... was just trying to finish dealing with a bunch of micro-particles.

Then my SWG broke. And I didn't notice for at least a full day, maybe two.

The pool had a bit of phos in it (300, not sure how bad that really is). Any, the result was a Green Swamp Monster.

So I dosed the pool (7000 gal) with bleach on repeatedly over starting Wed evening and through thursday, then started a full SLAM on Friday morning (managed to work at home that day).

I've been trying to keep the FC around 29, since the CYA is about 75.

But it's losing over 5 points of FC per hour. OCLT last night, FC went from 29 to 16 (9PM to 9AM).

So obviously it's consuming HUGE amounts of chlorine - I went through over 3 gallons yesterday, plus a left-over bag of hypochlor shock.

Is it normal for a SLAM on a 7000 gal pool to chew through chlorine that fast?

Any advice? Maybe replace some water to get the CYA down?

Thanks

 

[zea3]

I would drain and replace some water to get the CYA down to around 30. The slam will go quicker and use less bleach, although 3 gallons in a day is not a massive amount. How does the pool look today?

 

[bobandsherry]

Why are you using hypochlor shock? Is that acceptable based on SLAM method?

 

[domct203]

What the heck is ‘hypochlor shock’?

Perhaps you mean cal hypo?

You can use cal hypo, but it’s not recommended as it takes a while for the powder to completely dissolve, and adds calcium. The best thing to use is bleach.

 

[domct203]

Backstory: I got the pool mostly cleared up ... was just trying to finish dealing with a bunch of micro-particles.

Then my SWG broke. And I didn't notice for at least a full day, maybe two.

The pool had a bit of phos in it (300, not sure how bad that really is). Any, the result was a Green Swamp Monster.

So I dosed the pool (7000 gal) with bleach on repeatedly over starting Wed evening and through thursday, then started a full SLAM on Friday morning (managed to work at home that day).

I've been trying to keep the FC around 29, since the CYA is about 75.

But it's losing over 5 points of FC per hour. OCLT last night, FC went from 29 to 16 (9PM to 9AM).

So obviously it's consuming HUGE amounts of chlorine - I went through over 3 gallons yesterday, plus a left-over bag of hypochlor shock.

Is it normal for a SLAM on a 7000 gal pool to chew through chlorine that fast?

Any advice? Maybe replace some water to get the CYA down?

Thanks

What do you test with? A clean pool will not turn green in two days, I suspect you already had algae spores growing in the water.

Why do you think that the SWG is broken? If you have algae growing, the SWG will never be able to chlorinate the pool as the algae will consume it faster than the SWG can make it.

I also recommend you drain a bit and refill to get CYA closer to 30ppm. You will use way less bleach and it will be easier to maintain SLAM FC

 

[bobandsherry]

I would drain and replace some water to get the CYA down to around 30. The slam will go quicker and use less bleach, although 3 gallons in a day is not a massive amount. How does the pool look today?

I understand that with lower CYA the amount of chlorine needed to get to SLAM level is less. But since CYA reduces the FC burn off rate, if OP lowers their CYA wont that then increase how much FC is burned off by the sun? So while initial amount required to get to SLAM level is reduced, will the lower CYA just result in having to top off the chlorine more frequently and use basically the same amount of chlorine overall?

 

[domct203]

Right now the algae is the focus, which is being oxidized by chlorine 24/7 right now.

The SLAM process takes many things into consideration. SLAMming at 30-40ppm of CYA gives the best balance of UV protection vs algae elimination, while using less overall chlorine.

 

[dan52]

Thanks for answering, everyone

> Why do you think that the SWG is broken?

It's an Intex unit, 1 year old, and it's getting the low-salt warnings Intex is infamous for. Even after multiple cleanings, multiple salt-level checks, and reversing the polarity. The cells themselves are fine - it's the controller board. It'll run for a bit, with obvious chlorine in the output. After about 2 minutes it clicks off with the low-salt warning. I want to re-wire it to bypass the sensors, but can't find a diagram for the model ECO7110.

> Perhaps you mean cal hypo?

Yes. Calcium HypoChlorite. I'm not worried about adding calcium, the level is somewhat low.

> I would drain and replace some water to get the CYA down to around 30.

If I replace the SWG, I'll need bring the CYA level back up again, right? But not to 75 though, that's kinda high even for SWG?

Does the CYA level raise both the level needed and the burn rate? Or just the level needed? Or is it indirect - higher FC level increases the solar burn rate?

> How does the pool look today?

Honestly, pretty much the same as yesterday. It's pretty frustrating.

> ... 3 gallons in a day is not a massive amount.

Thanks. Knowing what to expect makes this less stressful. Guess it's time for another trip to Walmart, the 6 gallons I got is almost gone already.