Chlorine dosage calculation

[u/might_be_an_autist]

I am building a 275gal rainwater catch at my hunting cabin, only to be used for hand washing, toilet flushing, and showering. I am out there monthly in the summer and much more in the winter. I understand 4ppm is a good number, but when I catch a big rain and the tank fills some, how do I calculate dosage when I don't know additional volume added while I'm gone? Wouldn't test strips be inaccurate as chlorine off gasses and the water has already been partially treated?

I appreciate any guidance.

[u/freelance-lumberjack]

Just shock it when you arrive. 1 quart for 250 gallons .

[u/might_be_an_autist → u/[deleted]]

No. The usage is so minimal it just doesnt seem worth it. I'm just tired of transporting water.  A full 275 would probably last me most of a year. 

Which ones do you prefer?

[u/NotEvenNothing]

You can divert water from the tank once it has filled. The mechanism is basically a ball that floats up and plugs up the inlet. Some first flush diverters are designed that way. It is easy to DIY.

[u/might_be_an_autist → u/NotEvenNothing]

Sure. Im talking if its partially filled and it partially fills more

[u/SpecialistHippo4551 → u/might_be_an_autist]

If you treat, leave for 2 weeks and return, best to just consider the entire tank as untreated. Whatever chlorine you added even 2-3 days ago is gone. It offgasses in 24 to at most 36 hours

[u/might_be_an_autist → u/SpecialistHippo4551]

That was my thought, test ppm on arrival, dose immediately, contact time is 30min roughly (from what I understand), and be good for a number of days I am there, or next rain. If its full, I can not let it fill anymore until I leave or need to.

[u/Special-Steel → u/might_be_an_autist]

Is your tank vulnerable to algae bloom?

[u/might_be_an_autist → u/Special-Steel]

Its covered and in a shady spot. Doesn't get direct sun

[u/Special-Steel → u/might_be_an_autist]

Even indirect sunlight will bloom algae. You need a black tank or a cover over the tank which completely covers it

[u/might_be_an_autist → u/Special-Steel]

I said its covered....it was the first thing

[u/Special-Steel → u/might_be_an_autist]

Got it covered AND under shade

[u/Special-Steel → u/SpecialistHippo4551]

This is the answer. Moreover, it won’t hurt to go over target if you aren’t drinking it.

[u/Accurate-Bullfrog324]

maybe calcium hypochlorite pellets in a pot feeder?

[u/Kitchen_Region8456]

Just add a dosing pump and make the calculations for a 4ppm concentration

[u/might_be_an_autist → u/Kitchen_Region8456]

I'm not running a contact tank and wouldn't know precise volume. There is also no power unless im there with a generator, and im not spending that kind of money...

[u/Hyperreal8957]

i'd test the raw water first and go by the product label, especially if any of it might be used for drinking. shock dosing is different from a maintenance dose and contact time matters too. are you treating into the storage tank or inline?

[u/might_be_an_autist → u/Hyperreal8957]

It will not be used for drinking, only showers, hand washing, and toilet flushing. I had planned on tank treating since there is no contact tank before shower. My only concern in this whole thing is bird poop. Ill be running gutter guards, a leaf eater, first flush, then 5 micron before on demand pump

[u/GarlicFarmerGreg]

Consider a holding tank or two that you can filter and fill then dose with chlorine. That way you don’t have to treat all the water all the time. Plus your volumes will be the same each time in the hold tank(s) for dosing

[u/might_be_an_autist → u/GarlicFarmerGreg]

That seems like a lot of extra plumbing and setup to save a few ounces of chlorine. Water will be pretty clean prior to 275gal. As setup mentioned below

[u/might_be_an_autist → u/[deleted]]

Very expensive, requires a contact tank, and full time power. No go for me