Rainwater Harvesting

Reed_Richards

Has anybody looked at the economics of this? You collect rainwater (from your roof) in a big sealed tank. This keeps it fresh enough that you can use it for flushing toilets and washing clothes as well as watering the garden so you save money by cutting your water bill. The storage tank should last for decades but you need a pump which you have to replace every 5 to 10 years at a few hundred pounds a go. It looks to me as if you should eventually save enough to pay-off the installation costs but there may be expenses that I haven't taken into account.

in_my_wellies

My father has a huge galvanized tank placed on top of a stack above the garage. It's fed from the roof gutters and used to flush the upstairs and out house toilets, outside tap. In the past it fed a brass Victorian shower above the bath too. (He always regretted taking that out in the 1980s)

It's gravity fed, no pump

pinnks

Looked at this once but decided against on cost and disruption grounds - changes to plumbing to split the different cold water supplies etc.

Instead decided to focus only on harvesting rain water for the garden and occasional cleaning of PV panels and bought a used IBC tank that holds 600+ litres. It is fed from just one roof but apart from summer 2018 has not run dry. We could feed 3 more if we felt the need. Also bought a pump to allow us to power a hose for cleaning the panels and to avoid filling watering cans but to be honest have only used it a handful of times.

If anyone goes down this route I would suggest buying black IBC tanks (a little more expensive) as algae will grow in the white, translucent, ones within the first summer...

mmmmikey

Hi

I researched this extensively earlier in the year and I'm currently installing a 3000 litre underground tank to collect rainwater to be used for toilet flushing, laundry and watering the gardening. There are quite a few different options varying from DIY systems using secondhand IBC containers to underground storage tanks.

I decided to go for the "full monty" underground system at a cost of ca. £3500 - i.e. top end of the price range. This was an expensive option and includes a well engineered German pump / mains backup system. I expect to save about £200 per annum on water bills, so payback is about 15-20 years, not allowing for pump replacement. I have been told that a good quality pump could easily last that long, although the diaphragm would probably need replacing. This is a bit of a lottery of course, and any pump replacement or servicing costs will erode the financial benefit.

I should say that it probably only works for me by virtue of living in a bungalow (large roof area) and having high water consumption (WC flushing due to medical issues). Set against that, I do live in a fairly low rainfall area (ca. 600mm per annum).

So difficult to justify on purely economic grounds, but if you factor in the environmental benefits and possibly any value added to your property, in my view viable.

There a number of suppliers online, this is the one I used:

https://rainharvesting.co.uk/

Would certainly recommend them. Friendly, straightforward advice and competitive pricing. The kind of business you get a good feeling about and you would be confident in recommending to friends.

Be interesting to hear other views on this - make interesting reading in between bouts of back-breaking digging the hole for the tank

Hope this is of interest, Mike

EricMears

I've been using rainwater for flushing WCs since the house was built (we're just coming up to 19 years of living in it).

Installation costs were minimal - I started with two 'transitanks' which cost me nothing along with a water pump (also gratis). Added two extra tanks after a few years at £30 each. Tanks are in the basement on raised platforms which probably cost around £100 to build.

Water is pumped to two large (400 litres each ?) tanks in loft that I had to buy (prob less than £100). I don't really count all of that as part of the cost since even if I was flushing with mains water I'd always feed WCs from a header tank. Think about it (most builders don't !) : if you lose water mains and your WCs are mains fed you can only have one more flush until mains restored; with a header tank you'd have at least a dozen flushes (I'd have 6 weeks worth).

Adding an extra cold water circuit for rainwater cost something - but it was probably only around £20 of pipe (and I've still got more than that left over from the batch I bought initially).

Since we're on a water meter, costs are reduced by around a third (I've seen statistics somewhere suggesting that WC flushing accounts for a third of all usage). Not relevant in our case (we have a septic tank) but if we were paying for sewage disposal that would be based on water usage so also reduced by a third. Our water bills are around £100p.a. so we're saving about £50p.a. or coming up to £1000 worth of savings since we moved in.

The pump from basement to loft is now over 25 years old (it wasn't new when I got it) but still going strong and it wouldn't significantly affect my budget if I need to buy a new one.

But the reason for doing this wasn't financial ! I think it's a wicked waste to treat water to drinking standards then flush a third of it away.

pinnks

Couldn't agree more with the reasons for doing this and if one is building or refurbing it's a no-brainer but in a "normal" house situation the additional works are substantial and no doubt costly. At the end of the day that comes into each person's overall calculations...

silverwhistle

My water bills are <£200 p.a. and living in a terrace house there's not much incentive or opportunity to do major works. But there is no standard for new builds that reflects the future or how water stressed the south-east is.



I've a water butt waiting to be used for when the shed roof is renewed and guttering installed. Until then I put gravel trays underneath, collect water that way and store rainwater in builders tubs and assist the local mosquito population.. But I have thought of the additional storage an IBC would give me.


As it is anything one can do helps, and as an occasional angler I'd prefer the health of my local stream to more abstraction. Any tap I need to run, whether hot or cold, gets run into a bucket and straight to the garden. Flushing depends on need and whether I have visitors!

Reed_Richards

mmmmikey wrote: »

..So difficult to justify on purely economic grounds, but if you factor in the environmental benefits and possibly any value added to your property, in my view viable.

Pretty much my thinking, although I wasn't expecting any added property value.

mmmmikey wrote: »

Be interesting to hear other views on this - make interesting reading in between bouts of back-breaking digging the hole for the tank

I was hoping to avoid the back-breaking digging by getting someone else to install it for me, ideally someone experienced. But this seems to present a problem as the companies that sell the products seem to wash their hands of anything to do with installation.

gefnew

hi
use your experience to start a company that provides this maybe

Slinky

The previous owner of our house had installed a rainwater harvesting system, with rainwater and greywater from the bathroom going to a tank on top of the single storey extension roof. Our surveyor estimated it would weigh something in the region of a tonne, and the roof wasn't designed to carry the weight, so we had it drained and removed. The roofer who got rid of it cut it in half and struggled to get it down in 2 pieces, how they got it up in 1 piece originally is anybody's guess.

Reed_Richards

in_my_wellies wrote: »

My father has a huge galvanized tank placed on top of a stack above the garage.

Slinky wrote: »

The previous owner of our house had installed a rainwater harvesting system, with rainwater and greywater from the bathroom going to a tank on top of the single storey extension roof. Our surveyor estimated it would weigh something in the region of a tonne, and the roof wasn't designed to carry the weight, so we had it drained and removed.

I used to live near an old building with a huge rooftop tank; perhaps there had been a nursery there once with a requirement for a lot of water? But unless the building was purpose-built to carry the weight then a rooftop tank doesn't seem a good idea. A modern system would use an underground tank to keep the water fresh (and not get in the way) and a pump. You might have a header tank in the loft if you want to flush the toilet in the event of a power cut and save wear on the pump.