Why Refill After 6 Months?

[JackVa1]

There are only two of us using the Hot Tub. Water chemistry is good. Why refill?

Also : If I do refill now, should I use my Soft Water which will result in me adding Hardness or Bypass my Softener and use hard water which comes from a well and contains some IRON. Maybe I should use a blend?

Thanks

[Hillbilly Hot Tub]

There are only two of us using the Hot Tub. Water chemistry is good. Why refill?

Also : If I do refill now, should I use my Soft Water which will result in me adding Hardness or Bypass my Softener and use hard water which comes from a well and contains some IRON. Maybe I should use a blend?

Thanks

Because your TDS level may be high from the addtiona of adding chemicals. There is a test strip for TDS. Also if you use di-chlor you CYA may be high and if it is your chlorine is not working, even if you have a good chlorine reading. High levels of CYA will make your chlorine ineffective.

There is nothing like fresh water at a water change. It is a great feeling and well worth it IMO.

I would use the soft water and add calcium hardness. Iron is a pain and makes it so you need the addtion of other chemicals.

[Whoneedsavacation]

I wouldn't refill if the water is still pristine, but I find mine gets sluggish (air bubbles persist a really long time, looking cloudy) and foams excessively after a few months. At that point, refillling is like a revelation, the water is Soooooooooo nice. You don't need to do it for safety reasons, I think (eventually all the by-products of the chemical reactions that keep the water sanitary might interfere with the overall chemistry, but I think that would take longer than a few months) but for asthetic reasos, and for the life of the tub itself.

[waterbear]

Realize that every time you go into the tub you put a lot of perspiration in the water. Sweat and urine are almost identical chemically! The organics that build up quickly in a tub because of the high bather to water volume ratio is the reason to do water changes. I usually recommend once every 4 months!

[Nitro]

Becuase water is the cheapest chemical you can buy. The question should be, except for the winter, why not refill every month?

[tony]

Becuase water is the cheapest chemical you can buy. The question should be, except for the winter, why not refill every month?

Even though 500 gals of water will not break the bank, heating it to temp costs a bit. If your water is high in minerals like mine, then a bottle of Metal Gon is needed and if you use Nature2, there's another twenty bucks.

I usually change my water every four months, but my waters been so good that I've skipped a water change and will do so at the eight month mark.

[Nitro]

I guess I was referring to sometimes adding a ton of chemicals to get the water right, when it would be cheaper to just refill. But I see your point.

I'm lucky my tap water is well balanced, and in the summer on a sunny day heating isn't too costly. In the winter is another matter.

[chem geek]

As for how quickly water gets filled with chemicals that do not oxidize, that's very much a matter of bather load, cleanliness of bathers, and what chemicals you are using to maintain the tub. If you use Dichlor-only, then Cyanuric Acid (CYA) will often build up. If you use Dichlor for about a week and then switch to bleach, then you won't have that problem and the only buildup from chemicals will be salt (yes, regular sodium chloride like table salt). As for the ammonia and urea from sweat and urine, these will fully oxidize to nitrogen gas (and carbon dioxide gas). The chemicals that do not fully oxidize are the lotions and skin oils (and amino acids) that are more complex organic molecules. The use of chlorine or MPS will partially oxidize these so that they are dissolved in water (as Total Dissolved Solids), but for some of them their buildup could saturate the water making it dull or eventually cloudy (and form scum lines, etc.).

Note that if you do a test for TDS, that this will mostly be measuring plain salt since that is by far the largest component of TDS. You can't easily get a good measure of the TDS that is not accounted for by other parameters such as TA, CH and a salt (chloride) test. Some of the TDS chemicals are uncharged (neutral) so won't even show up in a conductivity-based TDS test. You basically just have to judge the water quality for yourself or use a standard water change rule such as:

Water Replacement Interval (WRI) in days = (1/3) x (volume of tub in U.S. gallons) / (number of bathers per day)

The "number of bathers per day" is more realistically "bather-half-hours" since a typical soak assumption for that formula is probably not more than 30 minutes. Of course, this is all approximate and the rule is a standard industry recommendation, not a requirement for residential spas (commercial spas will use the above rule or > 1500 ppm TDS rise from initial startup, whichever comes first).

Richard