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Smelly brown water from my rainwater tank!!

Posted by Barry Nutley on 4 August 2010 at 8:30 am

Q: Smelly brown water is coming through my rainwater harvesting system. I have been advised to add chlorine to the underground tank. What do you think?

A: Whilst that will work. It's not the ideal solution. Adding chlorine will probably solve the problem in the short term, but realistically you need to find out why it occurred. If you use the water for your washing machine adding chlorine won't do your clothes any good, and it's not that great for your garden either.

The ideal solution would be:

1. Check the gutters that feed the rainwater tank. Clear/clean any organic matter, there may have been a dead bird for example. If there were any of these, then the chances are, that was the problem.

2. Then check and clean your filters. Again, any sign of organic matter would suggest that this is the source of the problem. Remember, you do need to check your filters regularly.

3. Empty and clean the rainwater tank. This largely depends upon whether you've found the problem or not, the level of smelly water coming out, and what you use the water for. If for example, you use it for toilets/washing machine, then this would really be a must. However, if you only use it for garden irrigation, then it will probably correct itself (if the source of the problem were organic matter in the gutters or filters) over time.

Ultimately, you need to find the source of the problem. Remember, the tank in a rainwater harvesting system is pretty much a sealed unit, and it must have been contaminated in some way. Therefore, chances are, the cause will be found in 1 & 2.

Photo by Tabitha Hawk

About the author: Barry Nutley is co-founder and director of Viridis Energie Consultants

If you have a question about anything in the above blog, please ask it in the comments section below.

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3 comments - read them below or add one


stewartyardleyComment left on: 5 November 2013 at 7:30 am

I think the suggested answer given above is most likely going to be the solution that you are looking for. Since your rainwater system is pretty much sealed up and there is no other separate water supply, the root of problem would most likely be within the system itself and not externally. I think it is a dead bird too or worms and insects that might have fallen from the opening of the system. Do share with us your findings so that we can all benefit from it should anyone out there face a similar issue.

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Combined Harvesters Ltd

Combined Harvesters LtdComment left on: 5 December 2012 at 10:26 am


There are products out there that will help.  Along side a good maintenance programme.   Do you have a calmed inlet and overflow syphon on your system?

We manufacture a ‘Raincatcher’ rainwater harvesting filter that is impregnated with ‘Sprayguard’ antimicrobial treatment.

You can also use ‘Sprayguard’ direct onto your tank to prevent algea and microbial growth.

There are also products such as "Rainfresh".

Jemma Tunnington

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superkinradeComment left on: 15 September 2010 at 3:32 pm

Our rainwater harvesting system has been operating for approx. 3 years now and in that time a greenish film has built up on the walls of the toilet cistern.  I assume that this is biological and the build up, probably, inevitable given that we don't use UV treatment.  We have started to use 'Parazone' tablets in the cistern and the film is now beginning to break down and clear away.  I would be interested to hear from anyone else who has had a similar experience.

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