Poly 60, borax and algea

[chem geek]

Sodium Tetraborate Pentahydrate
Borax Pentahydrate
Sodium Biborate Pentahydrate
Disodium Tetraborate Pentahydrate
Disodium Biborate Pentahydrate

All of the above are synonyms for the same chemical. It is very similar to, but not identical to, Sodium Tetraborate Decahydrate that is found in 20 Mule Team Borax. The only difference is that the Borax contains more water attached to the borate. This just means accounting for that difference in terms of dosage (it takes a little more Borax).

If you were consuming a lot of chlorine, then you may have had a nascent algae bloom -- not yet visible, but using up lots of chlorine. Do you have any idea what your CYA level was when this happened? What kind of filter do you have and do you backwash regularly (not for cartridge, of course)? Do you have significant rains that cause overflow of pool water or significant splash-out?

I'll try and answer your questions as best I can. Some don't have unique answers and you'll have to make some decisions based on your own situation.

1) Borax is both a pH buffer and an algaecide. It also makes the water sparkle, as you noticed. It may not have been at sufficiently high enough quantities in your pool to be a fully effective algaecide. We recommend 30-50 ppm as you know and the detailed thread you referred to has links to EPA and other documents that describe the levels needed to kill various algal species.

2) It sounded like you were using algaecide before between the Optimizer (albeit, possibly in too low quantity) and "liquid algaecide" at least part of the time. Anyway, the short answer is that IF you maintain minimum FC levels appropriate to CYA levels (see Ben's Best Guess CYA chart), then you do not need an algaecide. However, in your situation since you aren't around often to monitor chlorine levels, then an algaecide is probably needed. I just don't know if having the 30-50 ppm Borates will be enough by itself to keep algae away at 0 ppm FC. I don't think we have enough experience with that. The use of PolyQuat 60 on a weekly maintenance basis (perhaps every other week) is most likely to keep away the algae even with no chlorine, but it's not cheap (but not as expensive as the Lithium Hypochlorite you were using at one point). Obviously, at 0 ppm FC, bacteria can thrive so you have to dose with chlorine and wait several hours (I estimate) before you go swimming again.

3) You need to test your CYA level to answer that question, but I suspect it's too high and you'll have to partially drain/refill and yes, go cold turkey. That leaves the problem of having some source of chlorine that will automatically be maintained when you go away. There are several options as follows:

a) You can use slow-dissolving Cal-Hypo tablets (though perhaps someone else can comment if they are really as good at slow-dissolving as Trichlor). That will raise CH, but that's not as bad as raising CYA and you only have to use it when you know you won't be able to add chlorine (or you can just partially drain/refill when it builds up too high -- maybe only once per year).

b) You can use chlorinating liquid or bleach in an automated injection system using a peristaltic pump. These are not common, but they have been used successfully.

c) You can add salt to your pool and get a saltwater chlorine generation system (SWG).

There may be other options I haven't thought of and others on this forum may have better suggestions.

Richard