Grrr - now I gotta SLAM (SWG timer failure)

[jeffbrig]

Looked out back yesterday and the pool had a distinct greenish tinge. Haven't seen that in YEARS following TFP. Well, apparently the old timer controlling my SWG stopped working. Naturally, it chose to do so in the OFF position. Not sure how many days it took, but the chlorine fell off, and with water temps in the 90s, algae can take off pretty quickly.

Interesting thing...in addition to the typical green film in places on the walls, I see something I haven't seen before. A bunch of small, dark, almost black, dots in the plaster that don't scrub off. I think it could be black algae. I'm sure my pool gets introduced to all types of spores with a freshwater lake maybe 20' away. Looks like I have my work cut out for me this weekend...

 

[PoolGate]

With the cooler temps around here and us not swimming as much, my chlorine has been drifting up into the mid teens. I have resorted to shutting off my SWG to allow it to get lower when this happens. I still check the chlorine level at least every 2-3 days and realized this morning that it got down to around 4. Just wanted to point out the importance of checking chlorine on a regular basis even with a salt water chlorine generator!

 

[jeffbrig]

Yeah, it's easy to get lulled into a false sense of complacency once the SWG is dialed in. Sure love having one though... beats the heck out of lugging chlorine jugs around to refill every week.

Morning stats:
pH: 7.5
FC: 13
CYA: <20 (bringing this up to 30)
TA: 60
CA: 300
SALT: 2900

Ordered a stainless steel 10" brush, figure that will work better than my combo bristle brush for getting the spots out of the plaster...

 

[Divin Dave]

Similar situation happened to me. I jumped all over it and slammed and cleared it up in about 2 1/2 days. I didnt have any black spots tho....

 

[Casey]

Are you even checking you numbers on a regular basis? Your CYA is very low for running a SWG.

 

[jeffbrig]

Are you even checking you numbers on a regular basis?

Define "regular", lol...
I test pH and FC pretty regularly. I test TA and CA far less often, and these numbers hardly ever shift in my pool - I have not needed to add calcium or baking soda in 4+ years.

Your CYA is very low for running a SWG.

Agreed - honestly I was surprised to see it was so low. I usually try to keep it in the 30-40 range. I know many suggest higher for a SWG, but I'm always gun-shy in case I ever have an issue and need to SLAM - the pool had excessive CYA when I bought the house. I typically only check CYA a few times a year - when I last checked it in the spring I added a little CYA to bring it up to around 40. Between splash out / overflow / and slow monthly decay, it certainly dropped faster than I expected.

 

[jeffbrig]

Similar situation happened to me. I jumped all over it and slammed and cleared it up in about 2 1/2 days. I didnt have any black spots tho....

And today the pool is back to blue and clear. Measured 16 FC and .5 CC this morning. SS brush arrives today - I'm gonna work on the spots over the weekend and then do an OCLT.

 

[PoolGate]

Define "regular", lol...
I test pH and FC pretty regularly. I test TA and CA far less often, and these numbers hardly ever shift in my pool - I have not needed to add calcium or baking soda in 4+ years.


Agreed - honestly I was surprised to see it was so low. I usually try to keep it in the 30-40 range. I know many suggest higher for a SWG, but I'm always gun-shy in case I ever have an issue and need to SLAM - the pool had excessive CYA when I bought the house. I typically only check CYA a few times a year - when I last checked it in the spring I added a little CYA to bring it up to around 40. Between splash out / overflow / and slow monthly decay, it certainly dropped faster than I expected.

Why are you gunshy about using CYA? CYA only gets in your pool if you add it. And it does degrade over time. I would get it up to 60 and maintain it there. It helps a lot on chlorine loss and general stability.

 

[jeffbrig]

Why are you gunshy about using CYA?

I didn't say it was rational...

 

[Casey]

You should at the minimum check all values once a month. That would have at least given you an indication of impending doom.

 

[RMcGirr83]

I'm under the impression that your SWG should be on the same timer as your pump for safety reasons (no pump no SWG). Is your pump not on the same timer?

 

[jeffbrig]

I'm under the impression that your SWG should be on the same timer as your pump for safety reasons (no pump no SWG). Is your pump not on the same timer?

My pump is a variable speed model with built in clock/timer/controls. I have it run at a high rpm first thing in the morning, low rpm thru the day while making chlorine, and high rpm again in the evening. The high rpm periods allow the suction cleaner to do its thing. My SWG is on its own mechanical timer and comes on during the day for about 5 hours to produce chlorine. Absent buying a separate controller, I don't know of a good way to tie them together. (There's also a flow switch on the SWG as a safety backup)

 

[RMcGirr83]

If your pump fails to turn on but your SWG does, then you stand the chance of having a catastrophic event (the SWG might blow up...literally). While I don't have a SWG, yet, I do have a VS that also has a built in timer/controls it still runs off the intermatic which I have set to run for 12 hours a day. It's pretty simple to tie the SWG and your pump into an intermatic if you're handy with electricity. When the intermatic hits the time to allow things to turn on, they'll either both be on or both be off. The flow switch is a secondary backup and shouldn't be relied upon as it is considered a fail safe.

Others more knowledgeable on the subject may chime in and refute me but that's what I gleaned is the correct way to ensure the two run together without having a catastrophic event occur.

 

[jeffbrig]

If your pump fails to turn on but your SWG does, then you stand the chance of having a catastrophic event (the SWG might blow up...literally).
...
The flow switch is a secondary backup and shouldn't be relied upon as it is considered a fail safe.

Yes, but the chance of that happening is very low, and a risk I'm willing to take. The flow switch is the backup/failsafe in case the timers ever get out of sync with each other, or the pump fails.

I would NEVER rely on a flow switch as the primary on/off for the SWG, but I have no issue with what I'm doing here. The few horror stories involving an exploding SWG that I've read involved a flow switch being incorrectly used as the primary on/off, and the SWG always energized.

The pump I have is designed to be constantly powered and run programs using its own internal clock. There small risk of an SWG issue isn't worth putting it on an external timer to me. We're all adults and can weigh the risk and make our own decisions...