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markpj23 · 26-02-2010, 05:02

I have a 100 gallon water tank that has been filled via our watermaker, hence no chlorine in the tank. I am concerned that the water will turn skunky as my consumption has been very low lately. I run the watermaker every 4 - 5 days to keep it in shape of course.

So if I want to add chlorine to the tank, how much should I use? Google search tells me all about how to shock chlorinate a well but that's not what I'm after.

Anyone have a table / reference that will get me to tap water chlorination levels (0.5 - 1ppm) for 100 gallons of water?

Kefaa · 26-02-2010, 06:38

Add 1/8 teaspoon (or 8 drops) of regular, unscented, liquid household bleach for each gallon of water, stir it well and let it stand for 30 minutes before you use it. Store disinfected water in clean containers with covers.

Per EPA Emergency Disinfection of Drinking Water | Safewater | Water | US EPA

Keep in mind at that level it also disinfects. As your water is good, you may get away with less. Unless the tank is contaminated.

In which case you need to clean the tank first. For that I used this Star San Sanitizer for Home Brewing based on a previous discussion on the topic of cleaning tanks http://www.cruisersforum.com/forums/...nks-31468.html

cdennyb · 26-02-2010, 07:34

be careful about adding chlorine to your tanks of fresh. If you have to store your watermaker, the chlorine laced fresh water in your tanks you use to flush it and pickle it will kill the membrane.

sailorboy1 · 26-02-2010, 08:00

I'm a water treater by trade. The problem with using a certain amount of bleach is that it will depend on the bleach strength AND on the oxdizer demand of whatever is in your tanks. So a given amount may do nothing if the water has already gotten a biological growth going. And just because you fill via a watermaker doesn't mean that there isn't a biological growth problem in your tanks (ROs have lots of bio-film growth problems).

I would go to a Home Depot or something and get a cheap chlorine test kit. Then go ahead and add the bleach as mentioned and adjust to get the 0.5-1 ppm of free chlorine out of the facet (that is a good number assuming you don't need to do a disinflection due to a bio problem).

And if you flush your watermaker from the tanks you need a carbon filter to take the chlorine out. For me I think I'm going to change over from bleach to peroxide for now on as I have easy source for it.

AnchorageGuy · 26-02-2010, 08:33

Don's comment is a good one regarding the flushing of the watermaker with fresh water from the tank. This will be hard on the membrane if the chlorine level is high. We had a 100 gallon tank and would shock the tank once a year. Once a month we added about 5 onces of household bleach to the tank and never had any issues in almost two decades. We did not flush the watermaker with fresh water until we had filled the tank the second time after treatment. Consider using White Vinegar as a regular treatment. WG

markpj23 · 26-02-2010, 10:29

Thanks for the replies. I have a charcoal filter plumbed in-line for the watermaker back-flush so all is well. At this point I have no tank contamination problem and just want to avoid one.

So doing the math I'll probably use 4-5 tsp for the full 100 gal tank. (Figuring 1/16 tsp per gallon, rounded up to 1 tsp per 20 gallons. It's less than 1/8 tsp/gal but I'm not sanitizing, just maintenance dose.)

Thanks everyone.

svHyLyte · 26-02-2010, 11:25

Mark--

Unscented Clorox Beach can be used at a rate of 1/2 teaspoon per 5 gallons of water. There are 6 teaspoons per ounce, hence for your 100 Gals, your looking at about 3-1/3rd ounces. We use roughly 1.5 ounces each for our 2-50 gallong tanks and seem to have no problems.

In re: a charcoal filter for chlorine removal, note that if the filter is not "fresh" it may not be particularly effective. If you can divert some of your product water away from your tank so that it is not contaminated, it might be better to use that to back-flush your system, per Spectra's suggestion.

FWIW...

colemj · 26-02-2010, 11:29

Mark,

Your tanks are aluminum and chlorine will react badly with them. I wouldn't add bleach, but pursue the peroxide route that Don mentions if you feel you need to. Another thought is to empty them and fill with municipal water for one cycle, which has some chlorine in it. Personally, I filter municipal water through a charcoal filter when filling to keep the chlorine out. Or even empty the tank down to 10 gallons or so and keep it at that level through use/addition. Then all water will be exchanged quickly.

If the tank gets growth, you can always shock it with chlorine - the chlorine won't be left in the tank long enough to do harm.

I speak from experience, you do not want to have to replace these tanks.

Mark

ConradG · 26-02-2010, 11:30

Don, could you elaborate on peroxide use? I don't mean to highjack here, but I think it might be relevant....

**Hud3** · 26-02-2010, 11:43

Mark,

If what colemj says is true, and you have aluminum water tanks, I strongly recommend that you not use chlorine. Island Packet used aluminum for a number of model-years, and we all had problems with white deposits of aluminum chloride forming in the tank and clogging up the freshwater pump strainers and the faucet aerators. I switched to 27% hydrogen peroxide, obtained from my pool maintenance company. It kept the water nice and fresh, and didn't harm the tank.

Careful with your dosage, though. Unless you want a blond wife!

ConradG · 26-02-2010, 12:07

Aluminum and cl....= poison gas....
What were you saying about peroxide Don?

sailorboy1 · 26-02-2010, 12:43

If you control the chlorine to less than 1-ppm it shouldn't have much effect on metals, even alumimum. But chlorine will always attack a metal (chlorides accerlerate corrosion in general). Some metals are really attacked by chlorine and all copper type "yellow" metals will suffer more. Alumumin is kind of special because people always associate it with corrosion resistance, but alum corrodes fast in a pH greater than 9. And since most water supplies are already in the mid 7s and sometimes 8s, when you add enough bleach to get the dose up you have increased the pH a lot.

Hydrogen peroxide is just water with an extra oxygen. You can do a lot of things with it depending on how you apply it. But for just biological treatment it works like all oxidizers (bleach is an oxidizer) where the high oxygen reduction potential basically "burns" organics out. But since it is just water and extra oxygen it doesn't have things like the chlorine that accelerate corrosion. And it will basically "flash" off out of the faceut. This of course is more complex, but hey this is a boating forum not an organic chemistry forum. You can get food grade hydrogen peroxide off the web and it will probably have a test kit available if you want to test for the level.

Back to the bleach; the sodium hypochite active part in the bleach varies. Industrial strength is normally 12.5% and chlorox is probably 3-5%. Either way it losses it's strength over time. So just saying add an amount per X-gals is of little use. You could add 1-gal and do nothing but tickle the biological bugs in your tank depending on how weak the bleach has become or how large the biological problem has become. If the water smells and tastes "skunky" it's going to take a bigger dose regardless. Even though chlorine will attack some polys, if you have poly tanks you would need to go out of your way to cause a problem and a taste test probably is good enough. If I had alum (or even stainless steel) tanks I would definitely be adding to a tested level. And remember even if you have poly water tanks you probably have a stainless steel hot water heater.

Bottom line - get the test kit!!!!!! You probably wouldn't consider swiming in pool that didn't have the correct chlorine treatment, why would you drink it! if you don't add enough to overcome the oxygen demand for the boilogical problem plus raise the level to around 0.5-1 ppm of FREE chlorine then you didn't get the job done.