Tue, 19 May 2026 14:42:11 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18079#Comment_18079 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18079#Comment_18079 Mon, 07 Apr 2008 10:57:19 +0100 Gary https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18108#Comment_18108 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18108#Comment_18108 Mon, 07 Apr 2008 19:57:01 +0100 Terry A smallish tank upstairs feeding loo's etc which when full then overflows into a larger tank outside for the garden. If the outside tank can be easily raised, then the garden can be gravity fed too.
New build would make this more feasable than retro-fitting.
obviously has structural implications(possibly offset by not having to dig a large hole, doesnt need pumps and electricity, .........
any other pros & cons anybody???]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18109#Comment_18109 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18109#Comment_18109 Mon, 07 Apr 2008 20:27:05 +0100 Bluemoon https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18115#Comment_18115 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18115#Comment_18115 Mon, 07 Apr 2008 21:30:44 +0100 John Pedersen
I have a 1500 litre tank on the ground. It costs me 7p to pump it all up to my attic ( I have one of those power meters ). I know this is a green issue rather than a financial one, but I live in the SW, and 1500 l of water from the mains would cost me over £6. The 7p represents a very small amount of power ( I was surprised - I expected it to be much more ).

I use a dead leg in the pipe, to catch gravel, some moss, and heavy stuff. Then the water goes through a pond-cleaning filter, which is just a tank filled with porous clay. The only problem I've had was a slight whiff in the water in autumn. It took an hour or so to clean the filter - and that's it. Almost all the water for the toilet, washing machine is rain water.

The pump was cheap - a submersible pond pump.

The rain water header tank in the attic fills from the mains if the rain water runs out - so you never know which water you are using unless you bother to check the tanks.

The whole lot cost £200 or so and it has been no bother. Oh, mesh on the gutters helps.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18128#Comment_18128 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18128#Comment_18128 Mon, 07 Apr 2008 23:29:29 +0100 Terry Agreed, not thinking from a financial angle, just trying to be practical in trying to avoid more bits of kit to look after, replace etc. If that is green too, bonus ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18168#Comment_18168 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18168#Comment_18168 Tue, 08 Apr 2008 19:14:37 +0100 Gary
Interested in your simple straight forward system. Where did you get the 1500l tank from? How does the clay filter operate and is this made by you or purchased.

Also in the SW so I understand the cost issue.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18177#Comment_18177 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18177#Comment_18177 Tue, 08 Apr 2008 20:11:08 +0100 John Pedersen
The filter was just a pond filter I found at the dump - I just washed the clay granules and started using it. The incoming water comes in the top, and a perforated pipe along the bottom under the granules is connected to an exit pipe which leads to the tank. The granules are probably 7 mm diameter, baked clay, porous. So they have a big surface area, which is colonised by bacteria. A coral reef fro bacteria! They eat whatever nutrients there are in the incoming water, leaving what goes in the tank fairly sterile and short of potential nutrient.

I'm in Totnes. If you're nearby, I'll show you around if you like. I'll probably replace the tank at some point - it is too much of a feature in my garden, and now I have a raised deck, I have somewhere more discrete to hide a collection of smaller tanks - those rectangular 1000 l tanks. The local winemaker has some.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18304#Comment_18304 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18304#Comment_18304 Thu, 10 Apr 2008 18:33:42 +0100 Albert The sytem planned will store 5-6000L, underground from a roof of 200 m2.
>Any views on helpful suppliers also appreciated.

You might consider looking at septic tank suppliers.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18312#Comment_18312 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18312#Comment_18312 Thu, 10 Apr 2008 18:56:31 +0100 Adam0734
I've lived in the UK and I've noted a few general differences:

1. We tend to maximize roof catchment (for obvious reasons) and so have a lower pitch roof (on average) than in the UK. We seldom have flat roofs. We tend towards hipped over gable, tho' historically we have used both styles.

2. Historically we placed water tanks apart from the main building, but current designs tend to put the tanks directly underneath the dwelling unit.

3. We don't have a clay soil (it's porous limestone for the most part) nor do we have significant seasonal variances, so we don't get the heave/subsistence issues that you have in the UK. This may influence our tank placement; I'm not sure. We do sometimes have a problem with thirsty trees trying to get to the tank, but this seldom causes significant structural issues. Build is strictly masonry.

4. We do sometimes have problems with tank leakage, particularly when the tank wall abuts a basement or similar area. Generally speaking it's not a problem.

5. We move the water through the building by means of a small pump, just as you seem to be planning to do. This system works well, but we find that we need to be wary lest the pump overheat through heavy use. This tends to be a real issue with the older pumps, not so much with the new ones. Be aware: if the pump goes, you have no water, and the pump usually goes at the worst possible time.

6. We tend to pay a lot more attention to our roofs & gutters than people in the UK seem to do. ;)

Now, as you're only using the water for gray purposes, you wouldn't need as big a catchment as we'd use. Moreover if you're converting an existing build you're probably limited to putting the tank in the back garden, where we'd position it under the house.

Keeping the water clear is the biggest challenge, but we tend to rely on pineapple filters up at gutter level to keep solid matter out. It helps that most of our trees are deciduous; not much leaf clearance for us. We also have tank air spaces to keep the water fresh - ie. we don't fill up to the brim, which might have a bearing on the whiff mentioned above.

In brief: not only is your plan feasible, but a similar philosophy keeps a country of 60,000+ in drinking water year-round. ;)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18409#Comment_18409 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18409#Comment_18409 Sat, 12 Apr 2008 18:34:45 +0100 jon
they are selling several of them (too large for me)

http://cgi.ebay.co.uk/Large-fibreglass-water-tank_W0QQitemZ120245261662QQcmdZViewItem?hash=item120245261662]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18450#Comment_18450 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18450#Comment_18450 Sun, 13 Apr 2008 10:44:44 +0100 Jane Smith
Our filter is a moulded black thing, like a small water-butt, with a plastic "washboard" cascade inside. Sorry, can't find a link at the moment.

We used a cheap submersible pump, again new, because neither of us know about making old things work!

It wasn't the cheapest way to do it but it certianly wasn't the most expensive. It all works very well, too. Apart from the odd occasion when the pipe vibrates off the end of the submersible pump. The toilets smell a bit odd when they flush for the first few days of setting it up, though that soon wears away.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18621#Comment_18621 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18621#Comment_18621 Tue, 15 Apr 2008 19:30:11 +0100 daysleeper
First off the tank design they provide has a large dead space, it has a circular cross section so with minimum depth for the pump to run there is a relatively large volume of unusable water in the bottom. Careful tuning can reduce this a fair bit but it takes a lot of faffing.
The pump pressure is an issue, its very hard to tune to the point where it runs when you want it to but does not blow all the seals in the toilets cisterns!
On the plus the pump is very powerful and can lift water a long way, had we known how good the pump is I'd have put the tank further from the house!
We have about 3000L underground storage for toilets and the washing machine (its the size the builder installed based on the advice from Envireau).... 5 of us in household its barely enough for 3 days without rain. I'm about to add minimum another 3600L in overground ex-orange juice tanks, mainly for garden veg plots. If I did it again I'd go for minimum 9K and preferably as big a tank as I could fit (no space issues so I could have had 10K plus tank).
There are 3 filters in the system, the main "leaf" filter sounds like Jane Smiths washboard cascade thing mounted underground near the tank. The pump has its own filter can (must remember to clean that) and there is a filter at the house entry which is easy to remove and deslime.
Other problems...leaves. We are surrounded by trees and I seem to be on a ladder every week to clean out the gutters.... think carefully about your gutters. have a good fall on them , the prat doing ours fixed them without any crossfall cos water finds its own level... yeah but the objective here is to capture as much water in a short period of time as possible!

Final point...overflow... shortly after we moved in on the odd very stormy night we have filled the tank, and the soakaway and then the driveway... a spot more digging with the JCB has sorted that but its worth thinking about when you start!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18635#Comment_18635 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18635#Comment_18635 Wed, 16 Apr 2008 06:02:07 +0100 Terry Apart from increasing storage, have you had a look at your rate of consumption. Seems very high for toilets and washing machine alone, or are you using it in the garden as well?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18639#Comment_18639 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18639#Comment_18639 Wed, 16 Apr 2008 07:59:25 +0100 jules
The calculation of monthly rainfall "collection" is apparently 1000 x monthly rainfall in m x roof surface area in m2 x 0.75 [for pitched roof] x 0.9 [for losses]. So for 100m2 roof and 60mm rainfall/month, you would collect 1000 x 0.06 x 100 x 0.75 x 0.9 = 4000 litres/month. That would give a recommended tank size of only 2400 litres. I guess that one issue is how regular your rainfall is - the more sporadic, the bigger the tank.

I have also read that the average person uses 150 litres/day, and that about 40% of consumption is on washing machines and loos. That would suggest that you would need about 70 x 30 = 2000 litres/month per person to be 100% self-sufficient.

Would be interested if anyone has different figures from the above, and also if anyone's used these people. http://www.rainharvesting.co.uk/index.html]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18690#Comment_18690 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18690#Comment_18690 Wed, 16 Apr 2008 21:45:18 +0100 daysleeper
Maximise storage is my advice. On rainy days the tank is full in very short order and from an economics point of view the brains of the system, digging the hole and plumbing it in are the expensive bits, bigger tanks don't cost too much more. Besides changing the tankage later is more of a problem... as I've figured out.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18726#Comment_18726 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18726#Comment_18726 Thu, 17 Apr 2008 12:46:29 +0100 Jane Smith https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18878#Comment_18878 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=18878#Comment_18878 Sat, 19 Apr 2008 11:41:20 +0100 John Pedersen
Even in summer, if we've been away, I haven't detected a smell in the water ( and my nose works really well!). The only smell we had was last autumn, when the filter was overloaded, but I don't mind cleaning that once a year.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19298#Comment_19298 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19298#Comment_19298 Thu, 24 Apr 2008 23:39:55 +0100 interested engineer
We are looking to develop a simple rainwater harvesting system that could be retro fitted to houses to supply just toilet flushing water, our target properties are victorian terrace houses and 1930's semis since these make up the bulk of the companies customers houses. Our focus is to reduce the runoff to the public combined / surface water systems and also to develop a product that is economic for the householder.

Our study of historic rainfall indicates that the 5% of annual yield figure used by the rainwater harvesting industry to size their tanks is an overestimation and that diminishing returns come into play very soon when sizing these tanks. This conclusion is backed up by a number of other previous studies. The reason being is that the bulk of the total depth of rainfall is in drizzly events not in the rarer more impressive deluges and the smaller events are easily contained in a small tank. To contain the larger events the tank sizes increase expenentially. Larger tanks simply fill up and then the available storage in a tank is determined by the consumption from the tank.

Previous studies indicate that existing commercial systems available today are unlikely to pay for themselves over any timeframe and given the embodied energy in the installation itself have quite dubious environmental credentials. One study indicates that in order to recoup the cost of a system within a reasonable timeframe water would need to be approximately £40/m3. Currently water / sewerage costs approx £2-3/m3.

There is also the issue of public health to consider and water becomes stagnant very quickly. Shorter storage time mitigate these issues.

The upshot of all this is that for a 2-3 bed victorian terrace where only the rear of the property is contributing to the system, say 50m2. The historic rainfall analysis indicates that there is little point in providing any more than 200-300l of storage since this will capture 50% of the total annual runoff and will save the householder approx £40 on their metered water bill.

I would welcome any comments?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19303#Comment_19303 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19303#Comment_19303 Fri, 25 Apr 2008 06:34:58 +0100 geegee
To ensure a high standard of public health what is the maximum storage time of water in a tank? Does this differ according to intended use or capacity of tank? Can this be extended somehow by treating and if so, would the energy required to treat it cancel out any environmental benefit of collecting it in the first place?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19307#Comment_19307 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19307#Comment_19307 Fri, 25 Apr 2008 08:33:07 +0100 Pete1951 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19372#Comment_19372 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19372#Comment_19372 Fri, 25 Apr 2008 18:30:05 +0100 John Pedersen
I am surprised at your estimate that water would need to be £40/m3 to get a reasonable payback time on a rain harvesting system. My system paid for itself in less than a year - though I did the installation myself. Another factor is that I have the roof area of and average semi, plus a garage, and a large extension.

Bit of a problem if you can only use half a terraced house to catch the water. One solution might be to use the rain water from all the terraced houses, and have one large tank for the lot of them.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19383#Comment_19383 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19383#Comment_19383 Fri, 25 Apr 2008 21:01:43 +0100 interested engineer
As you would expect some combinations worked better than others, but the most costly were simply a waste of time and needed a massive increase in the cost of water to deliver payback. For example a system costing £2000 installed (which is not untypical of some commercial systems) would need to save 1000m3 to return on the investment @ £2/m3. The average user flushes away approximately 30% of the average uk consumption of 135l/h/d, thats 40l/h/d or 15m3/annum. So assuming we had a 3 bed house supplied 100% from this system, it would take 22 years to payback. This assumes of course that the price of water does not rise in real terms. If you allow for spare parts, maintenance, dry periods etc the payback is complete blown off course.

Clearly this is based on a simple domestic UK installations where water is cheap, plentiful and secure, if you own a garden centre, nursery or car washing plant then the economics are different. If you live in Spain / Oz / LA then the reason for harvesting rainwater is for security of supply and in this case size really does matter.

This isn't all bad news, a simple gravity system, for example a 200l wall mounted tank feeding toilets with an automatic backup mains supply via a ball cock performed very well in the study, even in the smallest terrace applications. Its low capital, opex and installation costs made a massive difference to the economics.

The key thing is that the performance of a tank in terms of rainfall captured is not directely related to its size, for example, a 2000l tank does not capture 10x as much rainfall as a 200l tank. This means that in terms of payback it more more closely related to consumption.

Regarding retention times, there are no public health issues as such, water regulations apply to avoid back siphonage from the rainwater to the mains and provided these are observed things should be fine. The issue is more discolouration, smells etc, these are more dependant on how the water is stored, you could stick a blue block in the cistern to mitigate both colour and smell.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19846#Comment_19846 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19846#Comment_19846 Fri, 02 May 2008 13:58:59 +0100 Adam0734
We find here that the tanks need to be cleaned out on a fairly regular basis; you can get away with leaving it for a while (some do for decades) but the ideal'd be a clean-out every 3-5 years, and to clean (bleach) the roof every year.

One of our bigger problems is solid matter getting into the tank; dirt, mainly, but also animals, who are attracted by the smell of water, then can't get out of the tank, and subsequently drown & decay. You can fit pineapples over the gutter downpipes and grates over the tank air vents to prevent it, but maintaining the system is a fairly high maintenance job. Of course, we drink the water we catch; yours'd be a grey water only solution. Still, detritus in the tank may be contributing to the smell issues noted, which makes me wonder whether a regular clean-out might not be warranted.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19857#Comment_19857 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19857#Comment_19857 Fri, 02 May 2008 16:10:59 +0100 Miked2714 I'm very interested in your study, and I completely agree that economical systems are the way forward. Having investigated rainwater harvesting as part of building an extension, I quickly discounted underground systems, and will probably end up with a large water tank at ground level for the garden. I could use a pump but the kinds of pumps that can switch themselves when there's demand seem to approach £200. I'd have chosen manually-activated pumping to an attic tank as described by John Pedersen which enables one to use a much cheaper pump BUT one has to have space in the attic for the tank: we don't as we built in it.
So I've laid an independent set of pipework to WC's and washing machine, but my grand plan is currently lying idle (for a hydrologist this is very disappointing), hence my interest in your "wall mounted tank". Can you say any more about this? Is it internal or external. Or top secret?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19863#Comment_19863 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=19863#Comment_19863 Fri, 02 May 2008 17:10:00 +0100 contadino
Rather than invest in a new cistern straight away, my plan is to separate out the grey and black water wastes and reuse the grey water on fodder crops, and I also have plans to build a composting loo to realise some savings there.

In terms of financial savings, it's difficult to say as all country houses are off grid. However, we estimated that the running costs for a borehole would be EUR3,500/year, and the average (by asking friends) bill for mains water in town is somewhere in the region of EUR1,500/year (but obviously that's without irrigation demand.)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=20349#Comment_20349 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=20349#Comment_20349 Fri, 09 May 2008 23:03:49 +0100 kenavo https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=20363#Comment_20363 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=20363#Comment_20363 Sat, 10 May 2008 12:24:47 +0100 Katymac
Do you have to reinforce the rafters?

How much storage would I need for a roof about 140-150 sqm?

Will I still need to build soakaways?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=20367#Comment_20367 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=20367#Comment_20367 Sat, 10 May 2008 15:01:33 +0100 contadino
Salesman? Not here mate. Builders.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=21315#Comment_21315 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=21315#Comment_21315 Wed, 21 May 2008 14:28:58 +0100 telboy The system has an automatic top up feature and kicks in far to early losing a fair amount of the tanks capacity .Is anybody familiar with this system[what is it called ,how does it work]
I have telephoned the manufacturing ccompany in germany and they seem sure that the problem is the sensor unit and not the management system.
If anyone out there has any ideas or suggestions I would appreciate your comments .
Terry. P.S have tried lots of suggested ideas inc. cleaning the wires ,resetting the system etc. to no avail]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=21451#Comment_21451 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1545&Focus=21451#Comment_21451 Thu, 22 May 2008 10:36:35 +0100 Cliff Pope I recently upgraded the main tank from 1500 to 3000 litres.
in west wales the airstream is unpolluted, and we quite happily drink the rainwater without treatment. It tastes nicer than most people's mains water, but not quite as nice as that from the spring. There is a coarse filter in the collection hopper, to stop leaves etc, and the outlet from the tank has a finer marine-type filter with an access lid. Water is pumped up automatically as required to a standard domestic tank in the roof, normally straight from the well, but manually switched over to the tank when that runs low.
All the automation came from old washing machine water level sensors - one in the upper tank cuts in when the level falls, but turns off when back to the pre-adjusted level. There is one in the well to override the pump if the water falls too low, to stop it sucking dry. in that case a warning light comes on in the kitchen. The time it takes before the light goes out and the pump restarts is a measure of the spring's capacity. At most times it will pump continuously and never runs out, but in a dry season it can take several hours before the level has risen sufficiently for the pump to cut in.

The main pump has run faultlessly for 20 years, but I do have a portable 12 volt pump in reserve. Transfering water between the tanks on the different buildings a bit of a fag, but does at least give a measure of the extent of any drought, and a warning that we are running on reserve.
We use the compost toilet when water gets low.]]>