How much borax?

[TheOne]

I searched and couldnt find an answer...

I need to raise pH (mine is currently 7.0) without raising TA. I read waterbear's post about using borax and have a question about how much to use. By using the taylor base demand test it came out to recommending 4.7 lb of soda ash to get me to 7.4. How much borax would I need to equal 4.7lb of soda ash?

Thanks

FC - 5
TC - 5
PH - 7.0
CYA - 110
CH - 370
TA - 100


15250 gal IG gunite

 

[chem geek]

Re: How Much Borax?

I calculate that it would take 60.8 ounces weight (3.8 pounds) of Soda Ash / Washing Soda / Sodium Carbonate to go from a pH of 7.0 to 7.4 and that this would raise the TA from 100 to 128.2. It would take 120.4 ounces weight (7.5 pounds) of 20 Mule Team Borax to make the same change in pH, but the TA would only go from 100 to 115.5

Just multiply whatever weight of Soda Ash is required by 2 to get the amount of 20 Mule Team Borax that is required.

I calculated that using 4.7 pounds of Soda Ash would raise the pH from 7.0 to 7.53 so that really isn't that far off.

Your CYA level is very high even for an SWG system (they usually recommend 70-80). You are right to keep your FC at 5 ppm with that high a CYA level. I am surprised, however, at your low pH since an SWG system normally shows a rising pH. You also show having an Ozone system -- why is that? With an SWG there is very little need for an ozone system since it will just end up breaking down chlorine faster requiring you to run your SWG longer. The SWG should be more than sufficient at eliminating any combined chlorine. Are you adding non-chlorine shock (potassium monopersulfate) regularly or do you also have a floating feeder or other source of Trichlor tablets/pucks? If so, then that might explain the low pH and the high CYA (and both of these items, non-chlorine shock and Trichlor, are unnecessary with an SWG).

Finally, you indicate that the chlorine level is at 5, but what sort of test kit are you using? If it's a standard OTO or DPD color comparator kit, these usually only show a maximum of 5 ppm FC so your actual FC might be far higher. If you don't have one already, I suggest getting a Taylor K-2006 drop-based FAS-DPD chlorine test kit that will also test pH, TA, CH and CYA. I wouldn't necessarily trust your pool store's measurements if that is where they came from.

 

[TheOne]

Thanks for the assistance..I left out some important information...

New pool and the SWCG isnt active yet. I am waiting the 30 recommended days for the pool finish to cure before adding salt and turning on the swcg.

Powdered shock was added by pool builder I will need to check the specific chemical when I get back to the house. He left the bottle with me. I also saw the PB add 2 Gal of acid yesterday. The PB also added puck(s) to an erosion chlorinator while we wait to start the swcg.

True about the chlorine test. I did all the tests myself with the Taylor kit. I think its the 2005 kit but will need to check when I get home. Max reading is 5ppm for the chlorine test.

The paramount ozone system was "free" and obviously there is lots of mixed info about it. From the mfr/pb info I should be able to run my FC down to 2ppm while using the ozone system. Therefore they say I should be able to turn my SWCG output way down as not as much chlorine is required when using the ozone system. Time will tell on that.

 

[JohnT]

One thing I'd add about adding anything to tweak pH or alkalinity is to add half of what you think you'll need, then retest the next day. I've seen a lot of people chasing their pH around. Add half, and if it makes half the change you need, you're good to go. If it doesn't, you've only screwed up half as much as you could have.

Much easier to ease up on the numbers you want than to try to do it all at once.

 

[chem geek]

OK, this makes much more sense now. First of all, I wouldn't worry about the low pH because with a new pool that is curing plaster, the pH will go way up rather quickly as will your CH level (so it is already high for a new pool and will likely get higher). You should probably talk to your pool builder about what they want to do about pH during the curing process -- they may want it to be on the low side, but whatever doesn't void your warranty would be good to know. I suspect that they'll say to add acid when the pH gets to a certain level. If they don't give you any advice, I'd just wait for the pH to go up on its own and then add acid to keep it down around 7.5. At some point, you may need to lower your TA, but might as well wait until the curing is further along since it'll just be a battle fighting it.

As for the ozonator, it really doesn't let you keep lower chlorine levels then you are already going to have with the SWG. In other words, both the SWG and the ozonator do the same thing with regard to eliminating combined chlorine and free-floating algae so that less chlorine gets used up, BUT ozone also breaks down chlorine itself so you are working at cross purposes using an ozonator with chlorine, especially with an SWG that will already do most of what an ozonator will do. Remember that the chlorine in the pool water is there as a residual to fight whatever is in the pool and any pathogens or algae stuck to pool surfaces will not get "zapped" by either the SWG or the ozonator. I would not run your FC level below 3 ppm and would keep it higher than that until you get your CYA lower. Unfortunately, the high CH and CYA you already have indicate that you may need a partial drain/refill in your future (you don't backwash since you have a cartridge filter and probably don't have much splash-out).

 

[TheOne]

Thanks for the help. I will contact my PB to get their input on how to handle the low pH since I'm still early in the startup process. Also its an agregate finish pool and not plaster so Im not sure how that affects things...

Regarding the ozone system from what I understand the ozone system will function as a supplemental xidizer while the chlorine will continue to be used as the sanitizer. The Taylor book says when Chlorine is used in a pool only 10% is used for sanitation while 90% is used for oxidation. The theory is the ozonator assists in the oxidation so the chlorine can be more effective as a sanitizer. That is where they get the estimates of lower chlorine usage based on the supplemental oxidizer. Time will tell on that though I suppose.

 

[chem geek]

Well, you need to keep the Free Chlorine level the same (i.e. 3 ppm FC) in any case because of the need to have enough chlorine to kill pathogens and algae on pool surfaces that will never see the SWG cell nor the ozonator. The ozone in the ozonator lasts a very short time and does nothing to sanitize or oxidize anything that isn't free-floating in the water and eventually circulates through the ozonator. So let us know if you find that you can turn down your SWG output when the ozonator is used vs. not used. That would certainly be useful information to know.

So yes, you are right that organics that flow through the ozonator (which probably comes first BEFORE the SWG cell) should get oxidized and that would be less work for the chlorine to get used up later. So IF the organics oxidized by ozone saved more chlorine than the amount of chlorine broken down by the ozone itself, then you would need to generate less chlorine. However, the dirty little secret is that most chlorine doesn't get used up by killing pathogens OR oxidizing, but rather gets broken down by sunlight. Up to half of the FC gets used up in a day due to breakdown from sunlight and that's when there's CYA in use (without CYA, half the FC can get broken down in a half-hour with direct noontime sun). The amount used to oxidize organics is far less (probably 25-29% of FC), the amount killing or preventing algae is less (maybe 20% FC) while the amount killing pathogens is very small (maybe a percent or two of FC). The 90/10 rule applies to the FC usage that isn't broken down by sunlight -- so FC usage overnight or in indoor pools.

The main advantage of the ozonator is that it is one of the only methods (in addition to UV) that is effective against protozoan cysts (Giardia and Cryptosporidium). Chlorine is essentially not effective against cysts (especially Crypto). However, this is more of an issue for commercial pools compared to residential pools unless you are sharing the pool with those who are ill and carrying those protozoa. That is, these are not normal bacteria or viruses that typically get into residential pool water.

 

[TheOne]

The ozonator that I have (Clear O3) Paramount Pool Products Clear O3 actually uses a UV bulb to create ozone and injects it into the plumbing system. So its not inline with the plumbing per se where the water runs through the ozonator. I will check the install manual tomorrow to see if I can tell at which stage the ozone is injected, pre filter or post etc.

I agree that its affects may be limited as its only working when the pump is running while chlorine is obviously still in the pool all the time. Also it dissipates quickly so there is no residual affect. After my pool settles down from all the dust etc from startup I will see if I can tell if it makes a difference by turning the ozonator off for a week or so then turning it on.