SWG Can't Keep Up

[revv]

I'm having a strange issue. For the past few days, the SWG cannot produce enough chlorine. In the winter I ran it at 10-30% and it did just fine. I assumed that I would have to bump it up to 80% in the summer and it would be great. However, for the past few days I've had it at 100% and it cannot keep up. Last night I left the pump running at 100% and this morning I had gain of 1 ppm FC vs the previous evening.

I took some water to the pool store to make sure I wasn't going crazy and the results were similar.

	TF-Pro	Pool Store
FC	5.0	4.87
pH	8	7.4
CYA	60	72
Salt	3000	2863

Last night FC was at 4.0.

I ended up buying a small bucket of chlorine tablets and a basket to help the SWG. Is this what I'm supposed to be doing and will it cause any chemistry changes in the water other than FC increase?

Looking at my records, you'll see that FC likes to be around 6-7 ppm. I don't really know how could it be that this SWG can't keep up with chlorine production. There has to be something wrong here, right?

The cell is nice and clean, no buildup of any kind. Pump runs for about 8 hours a day at 2000 rpm. The water looks good as well.

EDIT: I just measured FC again and came in at 3.5 ppm. SWG ran all day at 80%, there is a tablet in the water (has been there since 11 am or so), and I still lost 1.5 ppm during the day. What is happening?

 

[SoCalTFP]

I'm having a strange issue. For the past few days, the SWG cannot produce enough chlorine. In the winter I ran it at 10-30% and it did just fine. I assumed that I would have to bump it up to 80% in the summer and it would be great. However, for the past few days I've had it at 100% and it cannot keep up. Last night I left the pump running at 100% and this morning I had gain of 1 ppm FC vs the previous evening.

I took some water to the pool store to make sure I wasn't going crazy and the results were similar.

	TF-Pro	Pool Store
FC	5.0	4.87
pH	8	7.4
CYA	60	72
Salt	3000	2863

Last night FC was at 4.0.

I ended up buying a small bucket of chlorine tablets and a basket to help the SWG. Is this what I'm supposed to be doing and will it cause any chemistry changes in the water other than FC increase?

Looking at my records, you'll see that FC likes to be around 6-7 ppm. I don't really know how could it be that this SWG can't keep up with chlorine production. There has to be something wrong here, right?

The cell is nice and clean, no buildup of any kind. Pump runs for about 8 hours a day at 2000 rpm. The water looks good as well.

EDIT: I just measured FC again and came in at 3.5 ppm. SWG ran all day at 80%, there is a tablet in the water (has been there since 11 am or so), and I still lost 1.5 ppm during the day. What is happening?

Have you done an Overnight loss test? Measure FC after sunset, don’t run your SWCG at night, measure again before sunrise (or at least direct sunlight). If you see over 1ppm FC loss something is growing in there and you need a SLAM.

It wouldn’t be shocking if your output was low at 8 hours a day, but I don’t know what cell you have. We’re entering peak UV summer so FC loss is going to be pretty drastic right now. I’d rule out something in there with the OCLT first, then adjust from there.

If it’s just low SWCG output you’ll need to raise % output first, then increase pump runtime. Since I’m assuming you have a VSP I’d just start running 24/7 until we can dial in your cell. You want a little output buffer so you don’t have to mess with you pump schedule automations for a pool party or something.

 

[mgtfp]

If the OCLT turns out OK then you can do as the next step the opposite, an Overnight Chlorine Gain Test, where you test FC after sunset and then let the SWG run at 100% over night until before sunrise, test FC again. Compare the the rise in FC over night with what you'd expect for your SWG for that runtime.

If that also turns out OK, I'd suggest to raise CYA a bit.

In you PoolMath logs you have a note saying "Ran MA through salt cell after mild calcification was noticed". What exactly did you do there?

 

[JJ_Tex]

I ended up buying a small bucket of chlorine tablets and a basket to help the SWG. Is this what I'm supposed to be doing and will it cause any chemistry changes in the water other than FC increase?

The pucks will add CYA as well. If your CYA is 60, you have a little wiggle room to increase the CYA but once your hit 70 I would stop adding the pucks and switch to liquid chlorine.

 

[mknauss]

Pump runs for about 8 hours a day

At 80% generation, that is adding 2.9 ppm FC per day. Depending where in CA you live, likely that is not enough.
Follow the instructions from the folks above and let us know.

 

[revv]

Thanks everyone and sorry for taking so long to reply, life got in the way.

I do think that what is happening is that there's just too much UV and the SWG needs help. It has been very hot today. Because I'm at the limit with CYA, this weekend I will switch to liquid chlorine. Should I SLAM to be sure there's nothing else in there? Can I use the pool during a SLAM with chlorine at something crazy like 23 ppm?

In you PoolMath logs you have a note saying "Ran MA through salt cell after mild calcification was noticed". What exactly did you do there?

That's just me cleaning out the cell in a bucket of water with Muriatic Acid

I think today was a bit better. I ran the pump all night last night and managed to get 1.5 ppm out of it as measured this morning. I only lost 0.5 ppm at the end of the day, but there's still a puck in the water.

 

[mgtfp]

OCLT will tell you if you need to SLAM. If you do - the water is safe to swim up to SLAM level for the respective CYA

Try to minimise cleaning the cell with muriatic acid as much as possible. Each time you do that, some of the Ruthenium cell plating gets removed, reducing the remaining lifetime of the cell.

Best to minimise scaling in the first place by keeping CSI slightly negative. If scaling does occur, try to remove it by spraying with a garden hose first. Then try to remove more with a soft wooden spatula or something similar. Next step would be cleaning vinegar which is not as aggressive as muriatic acid to the cell coating. Muriatic acid should only be the last resort, even though most manufacturers recommend exactly that in their manuals.