John Jackson Posted February 12, 2023 Share Posted February 12, 2023 Hello everyone. I would like to ask your advice. I have a 7500ltr underground rainwater harvesting and attenuation tank installed in the garden of my self-build. My initial intent was to pump water into a large header tank in my loft space, controlled by float switches, to feed toilet cisterns and washing machine. However, I’ve just realised that my locating a header tank in my loft may not be a good idea as the loft is within the insulated building envelope and will therefore sit at about 20 to 25 degrees C. These are apparently ideal conditions for Legionella formation. The reason for the header tank was to minimise pump cycling to prolong the life of the pump. Has anyone else come across this issue or worked out a sensible fix? Thank you, John Link to comment Share on other sites More sharing options...
Marvin Posted February 12, 2023 Share Posted February 12, 2023 I think you would only need a header tank that will hold about 2 days water at once. Ours is about 60 gallons. We only use rainwater for loos. held in a underground tank with the header tank filled daily and therefore doesn't sit long in the loft. However we do not use it for washing machines and only pass it through a sand filter. Link to comment Share on other sites More sharing options...
John Jackson Posted February 12, 2023 Author Share Posted February 12, 2023 1 hour ago, Marvin said: I think you would only need a header tank that will hold about 2 days water at once. Ours is about 60 gallons. We only use rainwater for loos. held in a underground tank with the header tank filled daily and therefore doesn't sit long in the loft. However we do not use it for washing machines and only pass it through a sand filter. Hi Marvin, thank you. Is yours a warm loft? John Link to comment Share on other sites More sharing options...
PeterW Posted February 12, 2023 Share Posted February 12, 2023 A floating hot tub chlorine dispenser would help you - just set it at the lowest dose possible Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2023 Share Posted February 12, 2023 Or just link the output from the pump to a cold mains accumulator vessel, and do away with the break tank altogether. https://pumpexpress.co.uk/shop/pressurewave-series-60-litre-vertical-pressure-vessel/ Link to comment Share on other sites More sharing options...
Blooda Posted February 13, 2023 Share Posted February 13, 2023 (edited) Our rainwater header tank is a cold loft. But think about it logically there are millions of open water tanks in "cold lofts" that are around/above 20 degrees for months on end in the summer months. 10 hours ago, PeterW said: A floating hot tub chlorine dispenser would help you - just set it at the lowest dose possible Potable water is less than 1mg/l, less than a teaspoon in 7500l Edited February 13, 2023 by Blooda Link to comment Share on other sites More sharing options...
Marvin Posted February 13, 2023 Share Posted February 13, 2023 Hi @John Jackson No ours is a cold loft but the insulation covers the tank. 9 hours ago, Blooda said: But think about it logically there are millions of open water tanks in "cold lofts" that are around/above 20 degrees for months on end in the summer months Yes it's the mix of water sitting for ages and the warm temperature that causes the problem. That's why I only have a small tank and refill it at the end of the day. When completing legionella risk assessments, water sitting in lofts for a long time was one of the problems. We had to make sure that any water connection changes that had been done over the years, removed all defunct pipework, that was still connected. Some buildings had long pipe runs to nowhere leaving water to stagnate for years causing a risk especially with mains water. Link to comment Share on other sites More sharing options...
John Jackson Posted February 13, 2023 Author Share Posted February 13, 2023 (edited) Hi All, Thank you for your responses. It's a new build house so will need to pass Building Control. I quite like the simple chlorination idea but doubt the BCO would wear it as it would need regular attention. I appreciate that many cold water tanks live in warm loft spaces in the summer but again, I think BC may have something to say about it living within the warm envelope. It will have to meet WRAS standards and I know that constantly above 20 degrees won't cut it. As for the pressure vessel idea, I think it's no different to a tank in the loft, it's just a different type of tank. Mmmm. I think this needs a bit more thinking about. Edited February 13, 2023 by John Jackson Link to comment Share on other sites More sharing options...
joth Posted February 13, 2023 Share Posted February 13, 2023 13 minutes ago, John Jackson said: It will have to meet WRAS standards and I know that constantly above 20 degrees won't cut it. Is that even possible? I thought WRAS is just for potable water; they require an airgap between anything carrying rainwater and anything being WRAS compliant, and the rainwater pieces are not WRAS compliant by definition. Link to comment Share on other sites More sharing options...
Blooda Posted February 14, 2023 Share Posted February 14, 2023 (edited) You're over thinking this. BCO probably wont even consider this, ours didn't even look at the tank. With difference in risk of legionella between your tank in the loft and a fish tank full of fish sitting in a living room? If you are concerned about being WRAS compliant, buy a proprietary system that is WRAS compliant [regarding the potable element], ours is from Rainwater Harvesting. It fills from the tank when there is water in the tank, and from potable water when there is none. it automatically recycles every three days when it is not used. There is an Air break between the Potable water and Rainwater. Edited February 14, 2023 by Blooda Link to comment Share on other sites More sharing options...
Blooda Posted February 14, 2023 Share Posted February 14, 2023 Further reading:- [ARCHIVED CONTENT] (nationalarchives.gov.uk) Section 7 Legionella species: A potential problem associated with rain water harvesting systems? - Judith A. Taylor, Rory McLoughlin, John Sandford, Ruth Bevan, David Aldred, 2021 (sagepub.com) "While there are a number of parameters and variations of this study which are yet to be explored, current data suggest that the risk of infection from RWH-fed toilets is very low but could be further improved with regular RWH tank maintenance" Link to comment Share on other sites More sharing options...
cwr Posted February 14, 2023 Share Posted February 14, 2023 17 hours ago, John Jackson said: Hi All, Thank you for your responses. It's a new build house so will need to pass Building Control. I quite like the simple chlorination idea but doubt the BCO would wear it as it would need regular attention. I appreciate that many cold water tanks live in warm loft spaces in the summer but again, I think BC may have something to say about it living within the warm envelope. It will have to meet WRAS standards and I know that constantly above 20 degrees won't cut it. As for the pressure vessel idea, I think it's no different to a tank in the loft, it's just a different type of tank. Mmmm. I think this needs a bit more thinking about. If it's just building control your are worried about why don't you phone them up and ask them? Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now