Changing Water - When?

[cramp11]

I'm 93 days into a fresh tub fill after a chemical detox. Everything seems fine, but if I should be changing my water I want to do it before something bad happens.

How do you know it's time to change the water? Do people just change it on a schedule or is there some kind of sign to look for?

I'd like to wait until the end of the month. I'm having the team over during hockey tournament and I'm sure it'll need a draining after that.

I remember reading somewhere on here that people try to fresh fill right before the cold weather kicks in and then try to last until the spring.

Again... no complaints about the current water...

I plan on doing a spa flush this time too since I've never done it.

[quantumchromodynamics]

Are you still on hydrogen peroxide?

What are all of your chemical readings?

[cramp11]

Doh. I didn't have the reply notification turned on.

I'm still using peroxide. I started a new thread since I didn't think that peroxide had anything to do with it.

I still don't have a test kit, but the strips show my pH and TA to be fine. h202 levels are well above 100ppm.

Back in November I had a sample of my tap water sent to Toronto. I just got the results today:

1. Appearance: Clear

2. pH: 7.01

3. Total Dissolved Solids: 301 ppm

4. Free Chlorine: 2.00 ppm

5. Total Chlorine: 2.00 ppm

6. If Bromine Pool: 4.50 ppm

7. Alkalinity: 260 ppm

8. Total Hardness: 260 ppm

9. Iron: 0 ppm

10. Copper: 0 ppm

11. Nitrates: 15 ppm

12. Phosphates: 300 ppb

Good? Bad? Alkalinity looks high, pH looks fine, but the rest doesn't mean anything to me. Clear is probably good.

Can I assume the same results when I refill my tub? I don't know how much serviced water properties change.

I saw another thread saying that TDS above 2500 or something means it's time to change the water.

[cramp11]

Ah ha! Found this in another thread

Water Replacement Interval (WRI) = (1/3) x (Spa Size in U.S. Gallons) / (Number of Persons Per Day)

I've had 56 people in the tub over 101 days

(1/3)x(290)/(0.5545) = 174

So I can ballpark about 174 days.

Since I keep a database on my tub, I might see about adding a formula to calculate WRI. At least that way if we have a lot of ppl in the tub, it will recalculate.

[chem geek]

Note that the WRI formula assumes something like 20 minutes for a soak -- 30 minutes tops. So if the soaks are for an hour, you get 1/2 to 1/3rd the time before water should be replaced. Remember that this rule is used for commercial/public spas. Also note that this rule may work reasonably well for Dichlor-only users, but that Dichlor-then-bleach users will likely be able to go at least twice as long between water changes. Since you are using hydrogen peroxide, I would expect you would be like the Dichlor-then-bleach users in terms of extended times between refills since you are not building up CYA in the water. In fact, you aren't even building up salt since hydrogen peroxide just breaks down to oxygen gas. So the primary buildup will be that of unoxidized organics.

[cramp11]

Thanks Chem.

I never stay in the tub for more then a cycle. (20 min) I guess it'd be 30 min if you count the time it takes to get in, get your drink, turn on the jets, etc.

That gives me a good baseline anyways.

What about using SpaFlush (or simular) with peroxide? I plan on using something, but I read that some have chlorine as an ingredient. I learned the hard way already that peroxide and chlorine don't get along. I don't want to pour the stuff in if it isn't going to do anything.

[chem geek]

I believe that Spa System Flush is mostly enzymes and not chlorine. Besides, you use it and rinse/dump the water anyway so should have little residual when you refill and use hydrogen peroxide again.

I believe I've discussed this before, but you do realize that hydrogen peroxide at the concentrations you are using (around 100 ppm) does not kill bacteria nor inactivate viruses quickly, right? This paper describes this in more detail with respect to E.coli.

There are two reasons why hydrogen peroxide is not an EPA-approved disinfectant for pools or spas. One is the slow kill times. The other is the instability in sunlight that, unlike chlorine, isn't moderated by CYA. As described in this EPA document which states the following:

Experiments have indicated that long contact times and high concentrations of hydrogen peroxide are required for bacteria and virus inactivation (Lund, 1963; Yoshe-Purer and Eylan, 1968; Mentel and Schmidt, 1973). Achieving a 99 percent inactivation of poliovirus required either a hydrogen peroxide dose of 3,000 mg/L for 360 minutes or 15,000 mg/L for 24 minutes.

Basically, hydrogen peroxide is an oxidizer, but except at very high concentrations, it's not a disinfectant. If you were to use concentrations of hydrogen peroxide high enough for fast disinfection, then it would be too irritating to the skin (in a hot tub).

[cramp11]

"hydrogen peroxide dose of 3,000 mg/L for 360 minutes or 15,000 mg/L for 24 minutes"

What ppm level is that? My tub is 1100L or 1200L.

I see a lot of sites that say to keep the level between 50 and 100 ppm. We've always been around 200ppm. Then again, we're using strips so who really knows. It's pretty easy to know if the levels are getting low. If you don't see air bubbles all over everything when you get in... it's too low.

The dealer says to add a cup every 4 days no matter what. Add more for heavy use. That's what we've been doing. If we're home (which we are 90%) of the time, does it make more sense to add 1 cup every 4 days or 1/2 a cup every 2nd day or even 1/4 cup per day? Small doses to keep the level the same or a heavier dose to spike the level?

We also talked about "shocking" the tub monthly with 4-5 cups just because. I don't know if that's necessary or not. Do you think it's a waste of chemical or a good idea?

I'm still going on the 5 gallon jug I got. I think I have about 12L left. Fingers crossed I don't get polio.

[chem geek]

1 mg/L = 1 ppm. milligrams per liter is the same as parts per million. Water weighs approximately 1 gram per milliliter so that is 1 milligram per microliter or 1 part per million since 1 microliter is 1/1,000,000th of a liter. So you are way, way, way lower than the levels quoted that are still very slow at killing pathogens and such levels would be way too irritating to your skin.

Since the hyrodgen peroxide is so poor at killing pathogens at the level in your spa, I can't say that shocking would do that much good since it would still be way off from what would normally be needed. You are simply taking a risk. It's somewhat like taking a bath without changing the water, at least from a bacterial or viral point of view (from a bather waste point of view, it stays fairly clean).

I'm just giving you the facts. There are no regulations of what people can or cannot do in their pools and spas. You could soak in raw sewage as far as the government is concerned. It's simply a spectrum of risk. Even water teaming with bacteria won't necessarily make you sick, but water that doesn't have bacteria (or at levels low enough for your immune system to handle) can't make you sick (from the bacteria).

[bart6453]

You could soak in raw sewage as far as the government is concerned. It's simply a spectrum of risk.

Not gonna lie....this made me laugh pretty hard!

[cramp11]

Thanks for the info...

I guess we'll stick with the 1 cup every 4 days. No spiking with 4-5 cups. Sounds like we'd just be wasting it.

I'll still probably drain it at the end of the month. (or once spring is finally here)

[SJ Hart]

Thanks for the info...

I guess we'll stick with the 1 cup every 4 days. No spiking with 4-5 cups. Sounds like we'd just be wasting it.

I'll still probably drain it at the end of the month. (or once spring is finally here)

Not very scientific, but I change my water when I get too much FIZZ in it (solids) that form when I turn on the jets. The water is always perfectly clear, but when the jets are running full I get fizzing like champange. Usually around 4 months.... SJ

[cramp11]

SJ Hart, are you using peroxide?

[SJ Hart]

I don't believe so. What would that product be for?

[cramp11]

SJ Hart, peroxide is the only chemical I use in my tub. Though it's not EPA approved, etc, etc... it's working fine for me. I just have to remember to add a cup every 4 days.

Day 124 and still crystal clear. Doesn't smell like sewage either. Actually doesn't smell like anything. Another reason why I like it. I go away for a week at the end of May. I think I'll drain it when I get back. I still need to pick up Spa Flush or a simular product.

[chem geek]

Note that I found that Australia approves hydrogen peroxide as a primary sanitizer in spas and pools. This page talks about how silver ions don't kill quickly enough and that hydrogen peroxide is a non-halogen alternative. Since it doesn't pass EPA DIS/TSS-12, it probably kills quite a bit faster than copper/silver, but not as fast as chlorine/bromine/Baqua.

[cramp11]

Interesting article.

I went to the page of approved peroxide chemicals. Curious to see if any of them can be found in Canada and how they are different then just the plain ol' jug of 35% peroxide.

[cramp11]

Draining my tub tomorrow. Bought a bottle of Spa Purge to see what it can do. All I can say is FOAM! Maybe I shouldn't have used the whole bottle. It's insane how much foam there is. I can't leave the jets on for more then a minute or it's overflowing.

http://easyspaparts.com/Spa_Purge_Instructions.pdf is an article I found. I gave it a whirl. Hilarious watching the foam come out the sides. Like adding regular soap to the dishwasher.

I hope the heck it all comes out when I drain the tub.

I'm not noticing anything floating around once the foam goes away. I guess that's a good sign.

[simonc]

Draining my tub tomorrow. Bought a bottle of Spa Purge to see what it can do. All I can say is FOAM! Maybe I shouldn't have used the whole bottle. It's insane how much foam there is. I can't leave the jets on for more then a minute or it's overflowing.

http://easyspaparts.com/Spa_Purge_Instructions.pdf is an article I found. I gave it a whirl. Hilarious watching the foam come out the sides. Like adding regular soap to the dishwasher.

I hope the heck it all comes out when I drain the tub.

I'm not noticing anything floating around once the foam goes away. I guess that's a good sign.

Just a comment on Spa Purge. I used it in my tub as part of a decontamination process and it did not do a very good job. After following directions and leaving it overnight, I got very little "scum" at the waterline ... similar to your experience. After the new fill, I still had a high chlorine demand. The next time I used "Spa System Flush" as the cleaner. I got a much more "scum" at the waterline. At least in my experience, "Spa System Flush" worked better than "Spa Purge".

Just my two cents worth ...

- Simon