Green Building Forum - Water Sat, 30 May 2026 11:02:41 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308621#Comment_308621 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308621#Comment_308621 Wed, 18 Jun 2025 07:50:03 +0100 Rex
There was a big head-line X days / weeks ago, that the gov are going to impose a planning requirement that every new build has solar panels installed.

All well and good, and certainly will please the Chinese panel manufacturers.

But one of my soap-box topics is that new building regulations should be that every new build has at least 3000 liter (and even considerably larger) rainwater collection to be used for flushing the toilet. It is complete madness that all water supplied to all dwellings is treated to drinking quality, but a large majority is flushed down the toilet.

That same collected rainwater can be used to wash the car or water the plants. Instead, planning application tick the 'environmental' box by installed a couple of water butts at the bottom of a single down-pipe. We installed a 6000 liter tank and with the dry weather at the moment, it is surprising how quickly it is emptied.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308622#Comment_308622 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308622#Comment_308622 Wed, 18 Jun 2025 08:20:31 +0100 djh
The complexity of water regs about using rainwater to flush loos, plus the practicalities of pumps etc and maintenance put me off even attempting it.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308623#Comment_308623 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308623#Comment_308623 Wed, 18 Jun 2025 09:01:04 +0100 WillInAberdeen
Toilet flush 5 litres
Leave sink tap running while brushing teeth 3 litres
Shower 40-80 litres
Bath 100+ litres
Dishwasher 10 litres
Washing machine cycle 50-100 litres
car washes/ water garden with hosepipe 20 minutes 100+ litres

Makes sense to collect rainwater for watering garden. I would ban outside taps, and make everyone collect rainwater instead. If you use too much and run out then carry a bucket from indoors, you'll soon appreciate how much it uses.

Not sure flushing toilets with rainwater is much better than window dressing. Same as the oft repeated thing about turning off tap while brushing teeth.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308625#Comment_308625 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308625#Comment_308625 Wed, 18 Jun 2025 10:32:33 +0100 Peter_in_Hungary Posted By: djhThe complexity of water regs about using rainwater to flush loos, plus the practicalities of pumps etc and maintenance put me off even attempting it.
+1


Posted By: djhI'd be happy if they connected up the planning law with the availability of sewage treatment capacity.


In Kent they have linked sewage load to the planning -

Quote
In Kent, "nutrient neutrality" for sewage means new developments must ensure they don't worsen the nutrient pollution of nearby protected water bodies like the Stour catchment. This often requires developers to prove that their projects won't increase the levels of nitrogen and phosphorus entering these areas, either through on-site measures or by funding off-site mitigation.
End quote

I was speaking to a Kent architect a short while ago and he said that because of the requirement to show "nutrient neutrality" virtually all new PP has stalled.

I understand that nutrient neutrality can be traded so a new build can get its nutrient neutrality by say installing a self contained sewage treatment plant on a property with a septic tank or using a change of use from residential to office use, both of which reduce the nominal calculated load and the freed up calculated nutrient load can then be used to support the new build.

Given the state of the sewage system in the UK if they connected up the planning law with the availability of sewage treatment capacity what would happen to the governments plans to solve the housing shortage??

IMO the sewage issues in the UK would best be resolved by separating the rain water from foul water systems.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308627#Comment_308627 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308627#Comment_308627 Wed, 18 Jun 2025 11:17:49 +0100 djh Posted By: WillInAberdeenSame as the oft repeated thing about turning off tap while brushing teeth.I haven't seen that mentioned in quite a while. But it would seem strange to run the tap whilst brushing my teeth, except for washing the brush afterwards. Specifically, you're supposed to leave the toothpaste on your teeth so the flouride can act. So turning the tap on before you finish brushing would seem pointless?]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308628#Comment_308628 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308628#Comment_308628 Wed, 18 Jun 2025 11:22:01 +0100 djh Posted By: Peter_in_HungaryIMO the sewage issues in the UK would best be resolved by separating the rain water from foul water systems.If that were practicable and affordable I'm sure they would do it. I believe it's done when new estates are built, but the effort and disruption involved in building a second rainwater disposal network and connecting up the many millions of rainwater systems that would have to be connected to it mean it doesn't happen for existing properties. We get a discount off our water bill for not sending rainwater through the sewer.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308630#Comment_308630 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308630#Comment_308630 Wed, 18 Jun 2025 11:45:28 +0100 Rex
TW are proposing a 3000 property development. Near by, there is a sewage plant that has recently expanded with a couple of additional tanks. But that more or less fulfills the requirements of all the new build site in the area and is most unlikely to be able to handle an additional 3000.

Fortunately, the River Wey is nearby so sewerage can easily be pumped there!]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308631#Comment_308631 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308631#Comment_308631 Wed, 18 Jun 2025 11:56:05 +0100 Doubting_Thomas Posted By: djhIf that were practicable and affordable I'm sure they would do it.

We had no choice but to combine them on our site due to ground conditions (heavy clay and close boundaries, so nowhere for soakaway).

In the end we agreed to include a water storage chamber to intercept flash flooding and release into sewer at a slower rate.

It was definitely expensive and I'd expect that UK ground conditions are so variable that it would be difficult to have a blanket country-wide mandate to separate flows.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308632#Comment_308632 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308632#Comment_308632 Wed, 18 Jun 2025 13:00:24 +0100 Peter_in_Hungary Posted By: djh
Posted By: Peter_in_HungaryIMO the sewage issues in the UK would best be resolved by separating the rain water from foul water systems.
If that were practicable and affordable I'm sure they would do it.
It is (or should be) practicable to build new sewage treatment plants and these should have been affordable but that hasn't happened either.

To me it makes no sense to have a combined rain and foul water system and whilst I accept that ground conditions will make this difficult in some areas there is as far as I know no effort to separate rain and sewage of the existing system where the conditions do allow for soakaways]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308633#Comment_308633 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308633#Comment_308633 Wed, 18 Jun 2025 14:45:58 +0100 Rex
Not sure what is complex about it. I did not go with float valves and various types of cut-outs, etc. I have a submersible pump on a timer and a loft tank for the toilets. Pump is set to run for around ten minutes every six hours to top up the tank.

If the water runs out, because I'm lazy, I usually know when there is no water in a cistern, then I unplug the pump and active the mains supply.

In the 15 years, I have had to replace the pump around one year ago as too many parts had worn out. But by that time it had exceeded its 'life' expectancy.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308635#Comment_308635 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308635#Comment_308635 Wed, 18 Jun 2025 18:17:24 +0100 djh Posted By: Peter_in_Hungary
Posted By: djh
Posted By: Peter_in_HungaryIMO the sewage issues in the UK would best be resolved by separating the rain water from foul water systems.
If that were practicable and affordable I'm sure they would do it.

It is (or should be) practicable to build new sewage treatment plants and these should have been affordable but that hasn't happened either.

To me it makes no sense to have a combined rain and foul water system and whilst I accept that ground conditions will make this difficult in some areas there is as far as I know no effort to separate rain and sewage of the existing system where the conditions do allow for soakawaysI don't think it's the cost of sewage plants that is the issue. It's the cost and disruption of connecting all the houses to a new pipe network, and of building that network. Soakaways aren't practical in most cases I suspect - not enough land in the right places.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308636#Comment_308636 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308636#Comment_308636 Wed, 18 Jun 2025 18:20:59 +0100 djh Posted By: Rex"The complexity of water regs about using rainwater to flush loos, plus the practicalities of pumps etc and maintenance put me off even attempting it."

Not sure what is complex about it. I did not go with float valves and various types of cut-outs, etc. I have a submersible pump on a timer and a loft tank for the toilets. Pump is set to run for around ten minutes every six hours to top up the tank.

If the water runs out, because I'm lazy, I usually know when there is no water in a cistern, then I unplug the pump and active the mains supply.Labelling on the pipework, air gaps, dual pipework and automatic system to switch to mains supply if no rainwater available (manual switchover not acceptable to SWMBO).]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308638#Comment_308638 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308638#Comment_308638 Wed, 18 Jun 2025 21:57:19 +0100 Artiglio
In respect of the neutrality rules, relatively recently and maybe still so, developers could offset from other sources. Apparently buying a trout farm or fishery and closing it down gave developers a massive amount of offset they could use. The sums of money involved were considerable.

My first job when i left school was as a builders labourer ( early 80’s) even then the norm was to have soak aways , extensions were expected to have them for the additional rain water, the exceptions were when the existing home already had a combined system AND there was insufficient space for a soakaway with the required speration distances.

Early 2000’s I built a small block of flats , that had to have a soak away chamber (no rubble fill). The surrounding buildings were largely 1870’s town houses, these had a combination of combined systems and soakaways, the soak aways built alongside the footings usually at the front of the building. I’m not aware of any of those buildings having had any subsidence problems with soakaways so close ( though i’ve never seen one that has been opened up to see how it was built)

A newbuild estate near me has it’s own “holding pond” for run off.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308639#Comment_308639 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308639#Comment_308639 Wed, 18 Jun 2025 22:14:12 +0100 philedge
I think toilet flushing accounts for around a quarter of daily consumption so a fair bit to be saved by using rainwater??]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308652#Comment_308652 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308652#Comment_308652 Fri, 20 Jun 2025 13:28:27 +0100 fostertom Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308679#Comment_308679 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308679#Comment_308679 Sun, 22 Jun 2025 14:07:34 +0100 Artiglio Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308682#Comment_308682 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308682#Comment_308682 Sun, 22 Jun 2025 15:22:34 +0100 djh Posted By: ArtiglioHaving stored rainwater without lots of filtering ,treatment and separation is going to make a mockery of all the legionairres requirementsI don't think anybody's suggesting drinking the stuff, or even bathing in it?]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308683#Comment_308683 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308683#Comment_308683 Sun, 22 Jun 2025 17:01:21 +0100 Rex
Certainly, the toilet cisterns get a bit of silt, but a bit of a clean and flush every few months and the cisterns are clean. I had no issues with regulations during the build; the BCO showed no interest. The collection tank overflows to the soak-away and he was happy.

The only downside of our 6000 liter tank is that the cost of the excavation, tank, concrete, pump etc was far greater than the cost of water and in my lifetime, will never pay for itself. But when the water table is dropping and there is too great a demand on the potable system, I feel good that I am doing more than is necessary.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308684#Comment_308684 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308684#Comment_308684 Sun, 22 Jun 2025 18:06:11 +0100 Peter_in_Hungary
I understand that concessions on the sewage charge is made if you have a cess pit or septic tank or you don't put storm water down the sewer but AFAIK there is nothing in place to manage the loss of income when customers use harvested rainwater to flush loos and run washing machines.

Am I correct in this or can someone advise me differently.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308687#Comment_308687 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308687#Comment_308687 Sun, 22 Jun 2025 20:05:27 +0100 djh Posted By: Peter_in_HungaryI understand that concessions on the sewage charge is made if you have a cess pit or septic tank or you don't put storm water down the sewer but AFAIK there is nothing in place to manage the loss of income when customers use harvested rainwater to flush loos and run washing machines.

Am I correct in this or can someone advise me differently.I believe you're correct, but I suspect that so few people bother with rainwater harvesting for toilet flushing (as opposed to for garden use) that it's not a material issue for the water companies.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308699#Comment_308699 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308699#Comment_308699 Wed, 25 Jun 2025 20:28:27 +0100 Artiglio Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308701#Comment_308701 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308701#Comment_308701 Thu, 26 Jun 2025 09:20:06 +0100 djh Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308702#Comment_308702 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308702#Comment_308702 Thu, 26 Jun 2025 12:55:13 +0100 Artiglio
As an example, i have a flat in a block of 6 that has a cold water storage tank that feeds some toilets in the block and used to feed dhw cylinders before flats were converted to combis as time passed. Cold water came direct from the mains. The council were advised to monthly testing of cold and hot outlet temperatures in flats ( best endeavours by contractor to gain access withstanding). Utterly pointless as cold was from mains and hot water was heated within the flat so any issues from the storage tank mitigated. That service is £1600 a year for that block, justified to the council as being “sentinel point testing” which it isn’t but council won’t query the recommendation and just rubber stamp it. Neither will they answer my emails asking why they feel it’s necessary. Especially given the risk assessor used a photo of a different tank room in his report.

That said, rain water collection in larger blocks of flats that directly feeds the toilets and any “topping up” from the mains occurs at the tank, with some sort of chemical dosing and filtering should be feasible.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308703#Comment_308703 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308703#Comment_308703 Thu, 26 Jun 2025 17:55:57 +0100 djh Posted By: ArtiglioDjh, i’d be very interested to see how that would be seen under a legionaries risk assessment if used in rented property. Especially in social housing where the extent of risk aversion is plain bonkers.I have no idea about rented properties or social housing and any rules that may apply specifically to them. Nor what a 'sentinel point' is nor its testing. Nor the specific difficulties of dealing with councils - the usual advice seems to be to contact your councillor.]]> Water https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308731#Comment_308731 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18310&Focus=308731#Comment_308731 Tue, 01 Jul 2025 18:56:14 +0100 Artiglio