GDay Youse All;
being fairly new to spaology I wonder whether the venerable members of the forum could shed some light on the following: We have a 4 months old LA spa with factory ozone generator, use a Nature2 stick in one of the filter bags and do our daily test strip and sanitising ritual with lithium chlorine. We keep it at 36 degrees, inside in an alfresco room with the cover on when not in use. We use the spa between two and five times a week, usually only with two, sometime four or five people. The water always seems to be nice, balanced, clean and good on the skin. BIG Q: Why would one want to do a weekly "shock chlorination" if the unit is nice and sanitised anyway? What's the rational behind this weekly shocking we read about so often? Cheers & Greetings from Melbourne

I don't shock if my water is nice. If you smell strong smells some chlorimines may have built up and you could then use a non-chlorine shock.

I also don't regularly shock by the clock. The stores tell us to do it a minimum of once per week, or after every 2nd use. That's excessive, and I think they're just trying to sell more product. I would rather not have all those chemicals in the water and on my skin, TYVM.

Just keep checking your water daily, and have it tested at the local spa store every couple of weeks.

Agree with the shock theory here. Once you know how demand affects your tub, that will tell you how to shock... but only to a degree. The use of test strips make folks forget that there is a relationship to Total Chlorine, Free Chlorine, and Combined Chlorine. Your pool or tub smells like a public pool or hotel spa because of the Chloramines as the previous post mentions. That's the Combined Chlorine that needs to removed with break-point chlorination -- super chlorination or shocking. You need to do this because combined chlorine cannot sanitize and the "stuff in your water" is constantly driving your free chlorine into the basement creating more combined chlorine. So, you chlorinate, it attacks the stuff in your water, creates more combined chlorine and leaves the "stuff in your water" untreated because there is no longer enough free chlorine and now you have MORE combined chlorine. So, you add more chlorine --- and the cycle continues.

Shocking breaks the cycle, kills everything by adding a great deal of Free Chlorine -- Free Chlorine gets consumed by the beasties in the water and they "die" until there are no more beasties to consume the Free Chlorine and then your combined chlorine falls to zero and your free chlorine when appropriately shocked, should fall to a desired residual level. It's really freakin' cool chemistry.

AGE

Agree " title="Very Happy" /> It's the combined ( sometimes refered to it as "Spent" chlorine) chlorine, which causes the smell. Most pool stores don't even know about this.