How to establish a dichlor/chlorine dosing routine

[999]

Water Boy,
That is exactly what I was after, thanks.

[chem geek]

Let me be clear on what you are saying. If three of us spend an hour in the hot tub, then it will consume 10 and a half tea spoons of dichlor??? Surely that is as much as most use in a week.

You can't spend one hour in a 104ºF tub, at least not being in the tub the entire time.  If you are in a 104ºF tub for more than 20 minutes, you increase your risk of heat-related illnesses and injury including heart attack, stroke and brain damage.  But if you did have 3 people soaking in a truly hot tub for a full hour, then yes without an ozonator it would take about that much oxidizer to get rid of your bather waste from your sweat and urine.  If you use less than that, then you fall behind and find that you can't hold a chlorine level in the tub.  This has happened over and over again with reports on other forums (mostly poolspaforum.com) and once people use the right amount of oxidizer they stop having problems with levels going to 0 and bacteria growing.

People who use the tub at high bather loads, so long soak times and/or several people in the tub, typically do not use enough oxidizer.  Such high bather-loads work better with an ozonator, but ozonators are only good for chlorine spas if you use the tub regularly such as every day or two.  The ozonator will cut down such oxidizer requirements by half or more.  However, in between your soaks if you don't use the hot tub for days then the ozonator uses up chlorine faster (though in a bromine tub it's the opposite where the ozone produces more bromine from the bromide bank you initially create and with MPS the ozone doesn't react with it).  Your high load but infrequent use pattern is better for a bromine tub that has an ozonator, but you don't like the smell, so the other alternative is an MPS-based system, but to not be irritating and to be sanitary that requires Nature² silver ions.

[999]

Thanks for everyone's participation in this thread. It has been interesting to hear differing advice and it is obvious that there are several different ways of skinning the same cat.  As always I will certainly consider all that has been said then make a decision based on all the information from various sources.

[999]

I am now at the end of my second week using chlorine, and my chlorine demand seems to had slowed down.

I am now putting in 2 tea spoons when we get out in the evening, and that seems to last all of the next day. If we don't use it the day after one teaspoon is sufficient.

Could it be that until the CYA builds up, the chlorine burns off too quickly and after adding around 20 tea spoons in the first week there is now some CYA that is making the chlorine it last longer. Any thoughts on this theory?

[chem geek]

That's possible in the first few days since there can be more chlorine outgassing faster without any CYA in the water since the active chlorine level is higher, but after a week I wouldn't expect to see much change from that.  More likely is that there were things to oxidize in your water and you just got caught up.  In any event, glad to hear that your chlorine demand is stabilizing.  Just note that by using Dichlor-only you will at some point notice that the water won't stay in as good shape and will need more chlorine to clear (i.e. shock) due to the CYA buildup making the chlorine less effective.  However, by the time that happens you might decide to change the water anyway.  If you want the water to last longer...well, we've already talked about that.

[pkillur]

I don't think i could use the cartridge that you mention because my filter doesn't have a centre section that comes off. It is fixed.

I am encouraged to know that there doesn't have to be a constant reading of chlorine.

My ozonator is always bubbling, even with the pump on.

I could be wrong, and one of the hot tub wizards here will tell me if I am I'm sure, but the "bubbles" are created by your circ pump going through a venturi valve, at which point your hose from the Ozonator is plumbed in.  This is how my tub is (I know, because I literally replaced it 2 days ago!).  When I turn on the pumps the green LED on the MCD 50 goes off - you only have so much "power" to go around.  If I have no heat on (as in, the tub is at 103, and doesn't need heated) and the 2 pumps are on low, it stays on.  The moment the heater kicks on with the pumps the power goes off to the MCD 50.

That is why spa-kits are expensive - because they have to measure what type of electricity goes where.  After a couple of years making my spa an enjoyable experience (my joke about it was that I got it from my in-laws and it was the gift that keeps on taking!) the ozonator typically does cut out.  At least that's my experience.

[999]

My hot tub has a circulation pump and one 2-speed jet pump. It is in 32 amp mode so that the heater Will work whilst everthing is on. I think my ozozator bubbles the most when the jet pump is off. It bubbles a little when it is on speed one and nothing (or possibly a little) when on speed two. So still not entirely sure if it is on whilst i am sitting in it.

[999]

The only sure way to know is to unscrew the front panel and see what happens to the light on the CD ozonator.