What If You Just Don't Need A Water Change?

[Dust]

So I was yacking about filters in another thread, and I realzied its been 7 months since I got my tub, and I'm still working on that original water fill.

With all of the talk of a fill after 1 month, and many people shooting for 3 month fills, well, while I'm proud of having kept my water in great shape for 7 months, is it possible that it isn't as good as I think it is?

Visualy, the water is always crystal clear, and smells like water with a hint of chlorine. We use a chlorine based salt generator, and the water has a tendancy of leaving your skin feel pretty soft (if dry).

It is almost always just my wife and myself using the tub, usually using it for a total of 1 to 2 hours per week (each, so 2 to 4 hours), and usualy in large blocks (an hour at a time continuos).

We wear swimsuits, but will hang up the swim clothes and re-use them for a week or two between re-washing. We wash swim suits with detergent. We don't rinse before the tub, but we will have always showered that day (again, with soaps, etc), but since showering probably have hair and body products on. My wife is a bit girly, and is always covered in lotions and potions.

Its a 400 gallon tub

TA sits around 100

pH floats between 7.2 and 8.0 (a by product of the salt generation is that it steadily climbs from 7.2... when it gets to 7.8, or 8.0 if I miss it, we knock it back down with an cap full of ph lowering chem from the spa store)

FC changes from day to day depending how the salt based chlorine generator is feeling... it is often higher than average, not uncommon to be sitting at 5ppm, though if we don't use it for a week it will climb up to 8 or even more, so then we plunk into it for an hour to help bring it down )

I don't remeber the CH number, but its in the "Good" portion of the test strip.

TDS was around 2100 as of last weekend when I last checked.

We prefilter all water that goes into the tub, and have done two partial water changes of about 12 inches depth (in an 8 footer, 400 gallon tub) to help lower our original too high salt content, over these last 7 months.

I don't know what my phosphate levels are like, but we use MPS fairly regularly, so that is the only thing I can think of that could be high.

The only two chemicals we've ever used in the tub are whatever is in "ph down" (dry acid?) "alkalinity up" (baking soda?) and mps. We have never added any sort of chlorine directly to the water.

And finaly, the tub is equiped with Ozone, and we use a "micron" filter that we replace every 2 (once 3, once 1) months.

SOOOOOOOO

after all of that, what I'm hoping to figure out is, could there be a "silent killer" lurking in our water that warrents a water change when everything seems really good / easy to balance / nice to soak in? Arctic (our spa's manufacturer) claims they have people using this salt generator system that do 12 month water changes, due to the small amount of chemicals used... but I'd really like to hear other's opinions on this.

Thanks all!

Dust

[chem geek]

Dust,

If you lowered the TA level and added 50 ppm Borates, your pH would be more stable. It's the same approach as used with the Dichlor-then-bleach method described here. People using that method often find that they can go about twice as long as normal between water changes as the water quality remains good since there is no buildup of CYA so chlorine remains effective.

In your case, the saltwater chlorine generator (SWG) is additionally oxidizing more bather waste faster via super-chlorination in the SWG cell. See my response to your post here as well.

Richard