There is an 8000 liter water tank on top of my house which provides water for the house.

Bacteria, fungi, algae, etc often start developing in the tank, giving unpleasant smells, etc.

This chemical seems to be chlorine based. According to the bottle, the composition is:

Sodium hypochlorite 5% max.

Sodium hydroxide 1% max.

Amine oxide 1% max.

I'm thinking of maybe putting 50 ml into the tank about once a week.

Nobody is drinking or cooking with the water. It's used for stuff like laundry, showers, washing dishes, etc.

I know it seems like a strange idea, but I live in the countryside in a developing country and it's not easy to find stuff here.

The water is ground water that we pump up there with our own pump.

What's gonna happen? Should I decrease or increase the amount? Or drop the idea entirely? (And maybe do something else?)

It's very hot here, maybe 40 celsius in the shade. This tank is in the baking sunlight.

  • $\begingroup$ Once a week is maybe too often. You don't use those 8000 l in a week, do you? $\endgroup$ – Ivan Neretin Jun 2 '16 at 15:28
  • $\begingroup$ @IvanNeretin Nope, we use maybe 800 liters per day. We top it up maybe once or twice a week. BTW, won't chlorine evaporate into the air gradually? $\endgroup$ – Revetahw says Reinstate Monica Jun 2 '16 at 15:31
  • $\begingroup$ Is your tank sunlight proof ? $\endgroup$ – ankit7540 Jun 2 '16 at 16:07
  • $\begingroup$ @ankit7540 Yes, it's made of 10 cm thick concrete and is covered. $\endgroup$ – Revetahw says Reinstate Monica Jun 2 '16 at 16:47
  • 2
    $\begingroup$ Could a foam fractionator and ozonation be an alternative for you? $\endgroup$ – aventurin Jun 2 '16 at 19:38

The product which you have mentioned in your post may have other chemicals like fragrance etc... which may make the water not suitable for washing dishes.  

You can purchase sodium hypochlorite (bleach) which is sold separately as powder or solution and add to the water tank. The concentration added to water tank is crucial.

You can use unscented / fragrance free laundry bleach solution also. This will be easier to find. If you get solution (6% solution of bleach in water) then you can add 40mL to the 8000L full tank first time and mix.

Then, say after a week when your tank has 2400 Liters full (using 800L per day ); you can add 28-30mL again and then fill up tank to full (8000L). (Approximate ratio is 1-1.5mL per 200 Liters of water).

Preventing algal growth:

  1. To prevent the growth of algae it is always recommended to prevent light exposure of stored water. Dark colored/black tanks do well. You can cover the manholes/ crevices through which light may enter the tank.

  2. Additionally, warm water aids in algal growth, so you can try to cover the tank with some tarpaulin etc... to prevent heating.

  3. Regular cleaning is important. Algae already growing on the inner wall of the tank is difficult to to deal with. Proper regular cleaning will help to remove such growth.

  • $\begingroup$ Thank you for this answer. Unfortunately, I have no idea how to get a hold of sodium hypochlorite here. But I understand the point about the other chemicals. $\endgroup$ – Revetahw says Reinstate Monica Jun 2 '16 at 16:54
  • $\begingroup$ @Fiksdal : In India it is not that difficult to get bleach powder or solution. $\endgroup$ – ankit7540 Jun 3 '16 at 5:00
  • $\begingroup$ But the product I mentioned in OP is bleach solution, no? $\endgroup$ – Revetahw says Reinstate Monica Jun 3 '16 at 5:02
  • $\begingroup$ Yes, the RinAla product is bleach solution but it also has some chemicals (specifically which I do not know), which gives fragrance. These chemicals may make the water not be suitable for washing dishes. $\endgroup$ – ankit7540 Jun 3 '16 at 5:05
  • $\begingroup$ How can we know whether a particular solution has extra chemicals in it? $\endgroup$ – Revetahw says Reinstate Monica Jun 3 '16 at 5:07

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