Does it matter if the salt cell PCB panel is broken or do I just test my pool daily?

[outdoorsgal]

Fred, no worries about hijacking my thread. I haven't been coming on TFP and it's a good refresher and always something to learn! I'm so far away from remembering all the details of testing since my hubbie took over job and he does it more the pool builder way, (although if there's a prob I jump in to fix it, at least with the knowledge I have), since I knew PB owes a free acid wash in October and we need to empty pool for them to fix some grout lines (another story), I was ok letting the pool go until then. From what I remember, does the TA effect the CSI? If that's the case, maybe that's why someone said not to worry about the TA so much, cuz it has to lower to get a lower CSI? Or, from what you're saying, maybe I'm remembering incorrectly?

 

[mgtfp]

I am a bit flustered though that when I asked about this months ago I was told "don't worry about the TA if the CSI is good" and now I am finding it really is an issue

I guess the point is, that in the end you will invest a similar amount of MA. You can either add MA just as often as required to keep pH in the right range for your CSI. Or force TA down by adding MA basically daily and aerate, to reach a level where you will have to add less MA on a regular basis than before. But you needed to add a lot to get there.

In the end it's a personal preference whether you want to get busy for a certain period to then be able to relax a bit more, at least until you have to top up with high TA fill water again. Or just keep adding what's required. Unless your CH and the water temperature is that high that you can control CSI only by forcing TA down - in this case you have to do it, otherwise it's a choice. The aeration can then also have the side effect of cooling your water, which also helps to keep CSI down.

 

[mgtfp]

From what I remember, does the TA effect the CSI? If that's the case, maybe that's why someone said not to worry about the TA so much, cuz it has to lower to get a lower CSI? Or, from what you're saying, maybe I'm remembering incorrectly?

Yes, TA does affect the CSI directly (EDIT: technically, it's the carbonate alkalinity part of total alkalinity, which is where the CYA-correction comes in - it's just easier to have a formula where you can enter directly the parameters as tested with a standard test kit).

So, if there is no pH-window left to get CSI in the right range, then you have to force TA down. Otherwise it's optional, it will widen your pH-window a bit and it will slow down pH-rise. But you have to invest a lot of MA in a short period of time to get there. Up to you.

 

[mgtfp]

I am using at least three times the MA than I did prior to using the cell.

There actually is on more, more indirect, factor, but it might actually be the most dominant in the pre- to post-SWG-installation comparison.

Without SWG, you were probably happy to let your CSI go up to +0.3, which allowed you to let pH rise higher, where it was closer to equilibrium-ph with a low rate of rise.

With SWG, you now want to keep CSI slightly negative, which forces you (with high CH and TA) to keep pH lower, further away from equilibrium where it rises much quicker. That's got nothing to do with the chlorination process itself, but just with the pH window you are forced to work with.

 

[Rattus Suffocatus]

No I am actually very retentive about my TFP and pool chemistry. The worst it ever tested with the SWCG in place was +0,2 and that was when I had a family emergency and it went two full weeks. I was bringing it down to -0.1 and letting it creep up to +0.1 most of the time. That was with a once a week acid addition... obviously doing it more often should tighten up that range...

I went from dosing acid from once a week to three times.. we will see. The pool was much more stable at a slightly higher pH without the SWCG, but I still like it better with. There will be times when it will need to go a week, though and it'll go higher.... I'm not going to lose sleep about it.

I have scaling issues with the hot tub as well, and I managed to get the TA down to 80 in it. Our water just sucks... like I said.. it does it in our toilets too.... Matter of fact the next drain and refill on the hot tub I might do a bit of a acid sponge bath on the fiberglass. It's not unusual here to see neighbors get the tile cleaners (bead blasters) in once a year here... The hot tub is seven months older than the pool though.....

 

[Rattus Suffocatus]

In the end it's a personal preference whether you want to get busy for a certain period to then be able to relax a bit more, at least until you have to top up with high TA fill water again. Or just keep adding what's required. Unless your CH and the water temperature is that high that you can control CSI only by forcing TA down - in this case you have to do it, otherwise it's a choice. The aeration can then also have the side effect of cooling your water, which also helps to keep CSI down.

So now that I have a little more time now-- I will address it. Since I see you are from Australia, most other places in the world have soft water compared to most of the US. Melbourne's municipal supply has 10-26 mg/L CACO3?!? That is what Google says? I'd LOVE to have that even for my beer brewing water! Nowhere in the US is water that soft... even in soft areas like Florida.

I get 11 PPM TDS out of my RO system total! So you have almost pure water there. We have about 250 PPM CACO3 (10 to 20 times as much!) and another 300 PPM of "other minerals", our pH is about 7.6 and my fill TA in the winter is about 130 and in the summer 180. It is worse than that in Phoenix. We are higher in elevation, cooler and much wetter than Phoenix. Because of that their water is worse in all respects. They also mix in Colorado River water which by the time it gets this far south has picked up a lot of hardness from the canals.

I had about 300 PPM CaCO3 hardness in the Midwest but the TDS level was about 300 PPM total...

So it's a completely different ballgame here than in Europe or Australia apparently.

Now you are in a hot desert as well, but maybe you aren't allowed to have these-- pools here have float valve driven autofill lines. I can turn the valve off to it, but I can't see a good reason to do that. In Tucson, water loss during the summer (and it's peak heat now and almost peak dryness) is about an inch and a half a day (cover off). That's about 3.75 cm a day water loss. This is why pools have something to refill them as standard.. it could only take a few days to get below the tile line and start damaging the plaster!

There isn't a service in the US that you could hire that will do maintenance to a pool more than once a week, either. Not that I know of. So almost every pool here is taken care of only once a week.

So.. we do have a different situation here from you... considerably. I could probably run any sort of CSI level with 20 PPM CH and never have a cell scale up! I don't think I'd do a plaster pool there either because I'd want to use that water to my advantage, but at the rate of your fill water increasing CH? It would take 20x longer to have it cause a refill from CH issues... Literally the damage we get in a year to the water from evap and refill would take at least 15 years there.

As for aerating and cooling the water.. it's quite effective to do this here for temperature and I have a couple of times, but it also causes scaling at the evaporation line from the local area having the CSI increase when it is done, uses a LOT of water and raises CH, TA and pH because of the large amount of evaporation. I try to limit doing that. And with the floor system, I really have poor options for aeration, if I need to get serious about it (and I may) I might have to build something to go into a return (which I have to turn on) to do it for me. I can really only aim the returns upwards now and turn them on, or use the silcox on the pump through a garden hose back into the pool. This actually works better..

One thought I have had in addition to running a soft water line to the fill (which is about $2000 and rip out the drywall affair) is to design some sort of acid auto doser to the fill. I won't give details of my thoughts.. maybe I'll patent it. It's a freaking good idea.

But I keep hearing that SWCG's are pH and chlorine neutral but in my case and the couple of others I know that have them locally that isn't the case. I don't believe it.

 

[outdoorsgal]

Fred, I'm sure this can be found on TFP site but one of these days I want to look into the machines that Leslies pool stores sells to lower pH. Sounds too good to be true and noone has mentioned it in passing here when discussing lowering pH so my guess is it's too good to be true, but I thought I'd bring it up in case you haven't looked into them yet.

 

[mgtfp]

So now that I have a little more time now-- I will address it. Since I see you are from Australia, most other places in the world have soft water compared to most of the US. Melbourne's municipal supply has 10-26 mg/L CACO3?!? That is what Google says? I'd LOVE to have that even for my beer brewing water! Nowhere in the US is water that soft... even in soft areas like Florida.

Yes, you are right. We are quite blessed here with our water quality. Very low in CH and TA. I actually have to increase CH with my plaster pool, especially during winter. But I still managed to get scaling in my cell while I was still following general industry advice and added baking soda to get TA above 100. And it took me a while to realize that the colour based pH-test doesn't seem to work for me. I am not actually colour-blind (I never failed one of those tests), but I seem to be challenged with different shades of orange/red. I suspect that there where many times where I thought that my pH was 7.6, but it was actually 8 or higher. I am now using an electronic pH-meter which has solved this problem for me.

I totally understand that you are in a completely different situation. I also understand, that the statement that SWGs are pH neutral (apart from CO2-outgassing that can get controlled via TA management) can get frustrating when it doesn't work out in your situation. The SWG is only pH-neutral in the ideal situation that all of the chlorine gas that is being generated by the cell, gets dissolved in the water and "does its job" in the water. That cycle is pH-neutral. It is not unusual that some of the generated chlorine gas doesn't get dissolved in the water and out-gasses straight away, and is later on missing to compensate the initial pH-rise (the one that is mentioned in that Wikipedia-article) by breaking down to chloride (either by UV or by actual sanitation/oxidation). In a situation where based on TA, CO2-outgassing would stop at a pH of about 8, out-gassing of 10% of the generated chlorine gas drove pH up to 9 within a month if not corrected with MA (assuming an FC-generation of 2ppm per day). Chem Geek explains that in this post (and the one further down in that thread):

The level of pH rise from carbon dioxide is limited by the carbonate alkalinity level (TA with CYA and borates adjustments). For a pool at 85ºF with 70 ppm TA and 80 ppm CYA and 3000 ppm salt, the pH rise would stop at around 8.0. In an SWCG pool, however, there can also be undissolved chlorine gas outgassing and this won't stop so the pH can continue to rise indefinitely though since pH is a logarithmic scale it will appear to slow down as the pH gets higher. If chlorine usage were 2 ppm FC per day and if 10% of the chlorine gas were outgassing, the pH would rise (from 8.0) to 9.0 after one month, to 9.4 after two months, and to 10.3 after six months. This is essentially occurring from the "lye" produced by the SWCG that isn't getting compensated by chlorine usage/consumption because some of the chlorine outgassed instead.

This 10% chlorine outgas assumption corresponds to the need for adding 2-3/4 cups of full-strength Muriatic Acid (31.45% Hydrochloric Acid) per 10,000 gallons per month so is not an outrageous assumption, though usually a significant amount of acid demand is from carbon dioxide outgassing which can be largely controlled via a lower TA.

And then there is the effect that with a SWG you have (with high TA and CH) to keep pH in a lower range compared to a bleach pool where you are not worried about scaling in a cell - that means you don't get the chance to keep pH in the ideal range regarding CO₂2-outgassing. You can then either just keep adding MA when required - but I understand that having to add MA 2-3 times a week or even daily is not always manageable if you have a job and family business to deal with as well. Or you force down TA by aggressive MA/aeration cycles. You will over time probably need a similar amount of MA, but by doing the aggressive TA reduction when you have time to do so, you widen your pH-window which might allow you to only having to add MA once a week. In that sense the TA reduction is optional (as long as there is a workable pH-window at all) - you don't necessarily save MA by driving TA down (especially not if chlorine out-gassing is the dominating cause for the pH-rise), but by doing so at a time when you actually have time, you can make the day-to-day maintenance more manageable at least by widening your pH-window. Reading Marty's post in this thread, he seems to keep adding MA twice a week to stop TA from rising and to keep pH in the required range. Another option might be an automatic acid-feeder.

You could work out if you have a lot of chlorine out-gassing going on, by turning the cell off and chlorinating with bleach for a week or so, but keeping pH in the range you would with the SWG running. If your pH-rise slows down again, then you probably really have a significant chlorine out-gassing contribution. To reduce that, you could try if running your VS-pump a bit slower helped to give the chlorine gas more time to dissolve before leaving the return pipe.

 

[Rattus Suffocatus]

Actually my CH presently isn't that bad. 325. That's low for many people. To much chagrin of my kids who I fetch to put the cover on and off, I keep my pool covered pretty religiously. So in just about a year, my CH went from the fill 250 to the 325 it is currently.. so if I can keep the rise to the about 100 PPM a year that I hope to, then I can save water that way. And frustration.

There are only two possibilities for what happened with me really... the High TA fill water just encourages the scaling when anything (evaporation, running 24V at 5A through it) changes the CSI upwards.. or that I might be running the VSP too SLOWLY for 7 of the nine hours it's running.. I suppose the Cl- might be outgassing, I do get bubbles from the floor system but there is the cell, (mounted vertically because my equipment pad is "squished" due to being on a narrow side wall)... about 20' (3.5m) of buried pipe to the floor system or returns. The one good thing I suppose about the floor system is that then in most cases it bubbles up through 3'-6' (1-2m) of water before hitting the surface. I don't suppose overall it's better or worse than anyone else's setup. I think the cell being vertical contributes to it, and Circupool states if there isn't enough water in the cell this could be made worse in their "Help Manual". I am thinking of adjusting UP the VSP about 100-200 RPM, actually.. but I decided to do it next season so I have a fair comparison to this year. Adding more acid to the mix more often is this year's experiment until November when it probably will drop to the point of shutting. It's still hotter than Hades here now though.. it's been an extra hot year here and maybe that's part of it.. I dunno.. last year was wet....when we were building the pool, of course.

But yeah.. TA probably. I might not have an issue going on. except for the TA, everything else has been factory specs and I have been doing a good job with my TFP (CSI) since the pool was fired up last year. I am not lying when I am telling you that the scaling on my pool after a year is better than every other 1-2 year old pool in the neighborhood. It's just bad here for that. I do run my FC on the high end of TFP... 6-6.5 though that should affect scaling.

The big fun comes this weekend when I clean the filters for the first time.. The PB put in what appears to be over sized cartridge filters (HOA requirement or I would have done sand). I have given up trying to judge when to clean them by pressure rise. I am at about 11 months now and there's been zero pressure rise at both low and high pump speeds... so it will be interesting to see how dirty the cartridges are this weekend.. wish me luck. Though I have to admit the hot tub filters stay pretty clean.. maybe I am lucky in that respect.

 

[mgtfp]

Most of the bubbles should be hydrogen anyway, it would only be a small fraction of the chlorine at max that might outgas - otherwise you'd be in trouble maintaining your FC, I guess.

Your return is certainly shorter than mine, I guess I have about 12m. Not sure if I'm happy about that, but it should be good in terms of chlorine gas dissolving in the water, and not much I could do about it anyway. But I'll have to wait for summer to see if lowering my TA really reduced my acid demand (which was never too bad to start with, never had to add MA more than once a week. But maybe I should have with the above mentioned pH reading problems...). In winter my cell is still running, but not very much, and I'm keeping pH a bit higher to compensate the lower temperatures influence on CSI. We'll see. It was only towards end of last summer that I was transitioning to TFP, so I don't have a real comparison yet.

Good luck with your filters. After summer I gave my sand filter a deep clean for the first time. It wasn't too bad, but not really a job I'm looking forward doing too soon again.

 

[Rattus Suffocatus]

Okay, thanks. I situated the pool so the lines would be reasonable short. Digging here is expensive because, maybe only Texas has harder soil then we do. I use an electric demolition hammer with a shovel bit to plant trees and shrubs here.

For TA I was hoping that since my pH is rising 3x faster now that the extra MA would take it down. I am finding that it does but the water wants to balance itself. So it's not a linear amount of acid. I still need to pput more in each dose than I am.

This weekend was one disaster after another (some were BAD), and even though it was finally cool enough on Sunday to work without turning into a strip of bacon, I had higher priorities than cleaning the filter. The odd thing is that the pressure hasn't risen at ALL since the pool was new, but I am homing in on a year so I need to do it. Maybe cartridge filters are like that? Next weekend or thereafter.. I swear... I still need to finish up my sun block fence for the front of the equipment pad too before then end of the season. I can then put my trailer in a permanent spot invisible to my neighbor who's been patient with me on it....It's been HOT here though... so I haven't gotten as much done on anything outside this year as I did last year.