Affect of low CH with SWG?

Jump to latest Follow Reply
ITR

ITR

0
Gold Supporter
Nov 8, 2014
323
Clermont, FL
Hey guys. I know CH is recommended to be 350-400 with an SWG and I'm wondering what the affect of having a lower CH is with an SWG. Here's the deal:

Woke up this morning and the new SWG (installed earlier this week) is reading high salt. So I'm off to drain. My CH is at 375, but I will say I have been fighting a few scale spots...so I presume that number might be high for my particular pool. Since I need to drain about 15% of the pool to bring the salt down...I have started the drain. To bring my CH down to 350, I need to only drain 6%. I know I can add CH to the pool...but since I'm having scaling issues...what affect does a low CH have on an IGP pool with an SWG?

Not once has the CSI been above .6...and this scale issue is my nemesis...so would having a lower CH be better...or would I risk some type of long-term damage to the plaster (which I definitely don't want)?
 
I have a vinyl pool, so let me preface that someone else may correct me. I believe the higher CH range for a plaster SWG pool is to allow the TA to be lowered to control pH while maintaining a tolerable CSI limiting damage to your plaster. Are you pretty good at keeping pH between 7.5 - 7.8? High pH will drive scaling if not lowered.
 
pH was constantly rising last year (new pool). Which is when the scale formed. It hasn't gotten worse this year. This year pH fairly constant with a slight rise over the week. I add about 4-10oz of MA each week.

So why wouldn't you go below 350? Trying to understand the "why"....does is suck the calcium out of the plaster?

And.... do I do two drains..or just one and then bring up the CH after the 15% drain?
 
In an SWG pool it is best to maintain a CSI below 0. Try to target your CSI around -0.1. In terms of absolute quantities, CH is irrelevant to an SWG, in fact, the lower the better. But, to a plaster pool surface, CH is important. So use CSI as your guide - adjust pH and TA to create a negative CSI. I would not try to lower or raise CH, just let it be what it is and adjust the other pool parameters.

For reference, my CH is 850ppm (other people on TFP have CH up near 1000ppm) and I get no scale in my pool and my SWG never has scale in it. I simply adjust my pH and TA to get to the CSI I want.
 
JoyfulNoise said:
In an SWG pool it is best to maintain a CSI below 0. Try to target your CSI around -0.1. In terms of absolute quantities,
Click to expand...

Got it. And I try to keep my CSI negative (to work at loosening the scale...although I think it's a lost cause at this point....and I'm not about to do a full drain/acid wash). In fact, CSI has been negative since November of last year. Good to know I'm on the right track. The SWG is new this week...I felt I had a good handle on the balancing up until I had to worry about salt. I thought I was putting in less than I even needed for the minimum...but the SWG is registering high...so I must have over done it.

Thanks for all the help guys.
 
Do you have a K-1766 salt test kit? This is the most accurate test. SWGs report salinity based on a conductivity measurement and they are not typically accurate to more than +/-400ppm. You need to make the SWG happy but it's good to know how far off the salt level is using a K-1766 test.
 
I don't. But from what I have been reading I will be investing in one. Right now I have been using strips (I know...I know...not accurate either...but it's what I had in the pool test basket).

You bring up a good point. When I get the kit I will need to calibrate the SWG.


Sent from my iPhone using Tapatalk
 

Enjoying this content?

Support TFP with a donation.

Give Support
Definitely have read that article...at least 20 times. I've never gone below -0.5. If you think it's safe to go down to -0.8, I'll give that a try. Just drained 3" off the pool and will see where it is this weekend when I do my full tests. I have been brushing with nylon (or some type of polymer) brush. I'll give stainless a try...I just don't want to damage the interior given it's only a year and a half old.
 
Thanks. I picked one up and will start using it. Another question. Before I added the salt, the pool was crystal clear. Now it's a bit cloudy. The salt was added about five days ago. I know you guys will ask so here are today's results:

pH: 7.8 (added HCL to bring it to 7.4 this morning)
FC: 5.5
CC: 0.5
CH: 300
TA: 60
CYA: 60

It's not horrible...I can still see the vents in the drain in the deep end, it just looks like a lot of dust is suspended in the water. Especially at night with the lights on. Also, noticed the water today had a bit of a viscous look this morning. Ran the pump for about six hours today and the filter didn't clear it out.

Any ideas?


Sent from my iPhone using Tapatalk
 
I hope you're not draining / refilling? A high salt reading doesn't matter unless it's not operating, so I would leave everything where it is. You may have overshot due to the salt that would have already been in the pool, but 3000/3500 ppm salt shouldn't be an issue.

If I see a tinge of cloudiness, it's usually after a storm or a lot of kids swimming. I add a quart of chlorinating liquid (to eliminate anything that got added to the pool), brush it, run the cleaner, and then run the pump on low 24/7 until the cloudiness is gone. I might run the cleaner again, or brush it again to keep the dust suspended, but either way just trying to get the dust to the filter as quick as possible and get my sparkle back. :)
 
The cloudiness could be impurities in the salt. For example, if you added 200 lbs of 99.5% pure salt, half the impurities are soluble and half are not, there's around 1/2 pound of insoluble impurities floating around. I think you'd see that in the water, especially with the lights on.
 
I think you guys nailed it with the insoluble impurities . It was clear this morning...then I started up the Dolphin again it stirred up what was in the bottom and got a bit cloudy again. I'll keep the pump on today so the filter can work more. Thanks!


Sent from my iPhone using Tapatalk
 
ITR said:
I think you guys nailed it with the insoluble impurities . It was clear this morning...then I started up the Dolphin again it stirred up what was in the bottom and got a bit cloudy again. I'll keep the pump on today so the filter can work more. Thanks!


Sent from my iPhone using Tapatalk
Click to expand...

You could try letting it settle again and then using a manual vacuum instead of the dolphin. Pushing a manual vacuum slowly around the pool will disturb the debris less.
 
Thanks for the advice, unfortunately I don't have one of those. I just have the suction powered automatic that the PB left me a while ago and the Dolphin. I would assume the other one, since it bounces and has "fins" on it, would kick up even more.
 
Okay..so I yanked the Dolphin and it was full of sand. Probably the dirtiest I have seen it. I have the filters soaking in dish soap now. Another question since I'm new to the SWG world (let me know if a new post would be more appropriate). I have been reading about people running their T-15 at 85-95% for 12+ hours. I went with the Jandy 40k AquaPure but if I recall, they have similar production (the Jandy is 1.25lbs/24 hours) I originally had mine on 85%, but it was over producing chlorine. Since I'm in central florida, the temps are in the mid 90s for a good part of daylight. I dropped it down to 25% production and run the pump on low for 3 hours in the morning and 3 hours in the evening and it has been keeping FC around 5 (CYA at 60). Knowing that the goal on PoolMath is 3-9, as long as FC is staying stable at 5...should I be concerned that I have it set at 25% for only six hours?
 
That's great and no, don't be concerned at all. At 6 hours run time on 25% and a 10,300 gallon pool, you're producing 0.9 ppm FC per day.

People on 12 hrs with an IC40 at 80% might have a 20,000 gal pool, little kids and teens in it day after day, and burn 3 or even 4 ppm FC per day.

Most people talk about 2-3 ppm FC extinction per day. The lowest I've heard was 0.5 ppm per day. It varies widely depending on bather load, use of a cover, amount of sunshine, duck poo, etc. etc. etc.

Don't worry. Be Happy :)
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply