Defective K-2006 Kit?

[PoolDoc]

Thanks, Waterbear . . . but I haven't seen that data. Could you email me (or post in the China Shop) the details on negative bromide / SWCG interaction?

Will adding some Borates be a better alternative over sodium bromide and polyquat?

Hi Droweye; I'm checking on the bromine / SWCG interaction, and will let you know, as soon as I have definitive info, one way or the other.

The "Once a Bromine . . ." pool page is is something I wrote 15 years ago, and is really only accurate with respect to pools on which BCDMH tabs (or other dimethyl hydantoin based forms of bromine) have been used. I revised that page somewhat to reflect those facts, but need to take it a step further. Where sodium bromide is used, on each conversion cycle (by chlorine) from bromide to bromine, a small portion of the bromide is permanently change to bromate. So over a period -- possibly a couple of weeks -- most of the bromide is rendered inactive.

BUT, there's no downside to using borates . . . unless your have a dog you want to breed who drinks daily from your pool or spa. (In that case, there's a small chance the dog might get enough borates to affect his fertility.) So, unless dogs are an issue, going with the borates is all good.

[waterbear]

Thanks, Waterbear . . . but I haven't seen that data. Could you email me (or post in the China Shop) the details on negative bromide / SWCG interaction?

Don't have the data on hand. It was just some manufacturer's warnings that had crossed my path that their units were not compatible with sodium bromide (and off the top of my head I do not remember which). It does not apply to all SWCGs (and I suspect it has to do with the cell electrode material since the some of the units made specifically for spas to generate bromine used carbon electrodes or possibly the fact that bromine cannot be stabilized by CYA and the cell cannot product enough to maintain a desired level) since I do know that the PoolPilot units are compatible with bromine and even give directions on the amount of sodium bromide to add to generate bromine instead of chlorine in their PoolPilot SoftTouch manual. However, they do caution against the use of hydrogen peroxide as a chlorine neutralizer and indicate it can damage their cell in their pool pilot digital manual.

I do remember a post on a different forum by PoolSean where he said to turn of the SWCG for a few weeks if adding sodium bromide as an algae treatment since the cell could not produce enough bromine to maintain a residual without turning up the output ant that would shorten cell life,which makes perfect sense.

[PoolDoc]

I talked to Sean and Richard about this, and have thought about this a bit. The consensus seems to be that it is fine to use bromide with an SWCG, but that you need to pay attention to what you are doing (like so many other things!).

1. Bromide / bromine does not damage SWCG plates.
2. Bromide DOES tend to increase LOAD on an SWCG because it de-stabilizes the halogen residual (which is, after all, the point of using it!)
3. Increased 'on-time', from whatever cause decreases SWCG life.
4. When using bromide, care must be taken to not overload the SWCG. This is more likely where the SWCG is switched by an ORP controller.
5. Bromide is primarily of benefit when CYA is very high (>100 ppm). If CYA is lower, simply adding bleach to raise the FC to an appropriate level would probably be a better choice.
6. When CYA is very high, adding bromide to achieve an free halogen residual may well be appropriate.
7. Uncertainties include the time it will take to convert bromide to bromate, and the appropriate bromide dose.

[droweye]

One last question about my current pool condition. Is it advisable to drain half of my pool and refill before summer starts due to high CH and CYA? My CSI is currently 0.08, suggesting that it's safe @ T= 60 F. The CSI @ T = 80 F is 0.26 which is still safe.

My only problem right now is that since installing the SWCG has a rising pH, which I'm lowering with muriatic acid every week. I've dug through the pool forum and one suggestion is lowering TA to 80, but I don't have a aerator. According to the poolcalculator my pH should lower by ~0.8 from half gallon of addition of 31% muriatic acid, but even doing that my pH only went down to 7.6 from 7.8.

I forgot to mention that in my region it has been recently windy, and this Monday we had a brief thunderstorm. This may have possibly have aerated my pool and raised the pH.

[PoolDoc]

Hmmh.

When I was making and selling testkits based on the K2006, I threw out the Taylor calculator to keep people from using them. Why? Because people got too focused on the "numbers" and not focused enough on the pool. The PoolCalculator is nifty in some respects, but in others, it's a even worse version of the Taylor circular slide rule calculator.

Do you have a heater? If not, forget about the LSI . . . it really is not very relevant to you UNLESS you plan to add some calcium (don't!) OR are beginning to show calcium scale at the water line.

but I don't have a aerator.

Yes, you do. It's called "the surface of the pool". It's just a SLOWER aerator than a bubbler or aerated jet. To lower your carbonate alkalinity (the major -- but NOT only -- component of your TA), you just need to lower your pH to 7.0 - 7.2 and keep it there.

By the way, there are several theories about why SWCG's have been associated with upward trends in pool pH. As far as I know, NONE of them have been proven to be correct, so far.

Do you need to drain and replace, to lower CH? Dunno. If you aren't adding calcium, the ONLY reason your calcium level would go up, is if there's a lot of calcium in the fill water, and you are having a lot of evaporation. A good place to start, is by testing the calcium levels in your fill water.

According to the poolcalculator my pH should lower by ~0.8 from half gallon of addition of 31% muriatic acid, but even doing that my pH only went down to 7.6 from 7.8.

Yeah. Well. Don't believe everything you calculate. In particular, it's rather hard to predict pH change unless you have REALLY accurate info about where you are starting from . . . and you don't. There's a pretty good chance your 31% muriatic really WAS 31%. And, if it was, your pool pH decreased EXACTLY as much as CORRECT calculations would have shown IF you'd had ACCURATE numbers for your individual buffers (carbonate, cyanurate, borate?, phosphate?, what?), your gallons, and initial pH.

Again, this is why I prefer the DT method of dosing (Dump a reasonable amount in, then Test to see what happened. Repeat if needed) instead of the TCMD method (Test accurately, Calculate carefully, Measure dose exactly, Dump it in and then be surprised when the results aren't as expected) presumed by the PoolCalculator.

Let me say it again, differently: if the PoolCalculator (or any other pool calculator) were perfect, and was given perfect information, it would ALWAYS precisely predict changes. But, that's not going to happen with real world pools, chemicals, test kits, and pool owners.

So, why don't you do this:

1. Lower your pH to ~7.0. Ignore the PoolCalculator; just add muriatic acid 1/2 gallon at a time, till you get close, and then 1/4 gallon at a time.

2. Test your FILL water CH, and report that.

3. Buy 16 boxes of borax (8 per 10K gallons). Buy 1 gallon of 31% muriatic (2 gallons of 15% ) per 4 boxes of borax, PLUS 1 extra gallon. (So, 5 gallons of 31%). Add 1/4 of your acid. Then add 1/4 of your borax. (So, 4 boxes of borax & 1 gallon of acid). Wait 24 hours, then test. If your pH is low, add 2 boxes of borax. If it's high, add 1/2 gallon of acid. Wait, retest. If your pH is OK (7.0 - 7.8) add the next 1/4 dose. Continue till your done.

4. Order some borates test strips from Amazon.

5. Let us know how it goes.

(By the way, the TCMD method works really, really well for extremely accurate and careful people, like Chem_Geek. The DT method works better for most pool owners. If taking care of your pool is your hobby, use the TCMD method. If you are more interested in USING your pool, use the DT method.)

[CarlD]

I don't know if I missed it but I thought PoolSean said higher CYA levels don't harm SWCGs--just keep the 5% ratio of FC: CYA, so 180ppm would require FC=9, wouldn't it?

Remember dumping and refilling half the water will require more salt added for the SWCG, too.