Rainwater Harvesting...

[Mulberry View]

Any advocates of Rainwater Harvesting on here? I know some see it as questionable from an ROI standpoint, but for us it's not just that we're interested in. The idea of using rainwater to flush the toilets, to reduce limescale (we're in a very hard water area) is of interest. We might also like to use it for the washing machine. But being able to water the garden, specifically the lawn, in a guilt free way is the main driver for us.

 

We would also benefit from some eco-friendly water input as our water consumption data is a little over what was specified in planning (105 litres per person, per day).

 

But what size tank should we look at? We've got about 150sqm of roof space roughly 50/50 over 2 roofs. At the moment, only one roof is designed to go to a Rainwater tank, with the other is going to a normal soakaway. I'm wondering if we should harvest it all, maybe with a larger tank, or perhaps with a second tank? (one close to the house, one for the garden/car washing etc.)

 

Any help is appreciated.

 

[Nickfromwales]

When the garden needs watering, the tank will be empty. When the tanks full, it’s because it’s raining……on the garden. 
Same argument about using PV to run the heat pump for heating in the winter. 
Both = 👎. 
 

If you can fit a huge ( 10,000L ) tank to catch every single drop of rain then I’d say you’d be in with a chance, but a system that flushes the WC’s and washing machine will also have a cold mains fill valve to keep the head of water a minimum of 100mm above the pump inlet, so once you get down to 1000L in a 5000L tank you’ll be back to using fresh water eg a 5000L tank is a more closer to a 4000L useful capacity. 
 

When the pump snuffs it you’ll be back to a break even of 20+ years. Add to that the electricity to run the pump all the time your flushing loo’s / watering gardens / washing cars etc and the maths ( and longevity ) go negative.

 

Spend the money on something that will give you enjoyment, like lots more solar PV, so you can wave a smug and satisfying 2 fingers at the big 6. ✌️

[SteamyTea]

A lot of it will depend on how much you pay for water and waste.

I pay a lot.  The most expensive in the country.

If I had more room outside, I would fit something.

[Gone West]

33 minutes ago, Mulberry View said:

being able to water the garden, specifically the lawn, in a guilt free way is the main driver for us

At our last house, with the same low rainfall as your area, we used our accidental borehole for watering the garden. It was very useful and if you are able to install a large enough tank I would do it. If you like gardening you will probably end up using most of it for the garden. We were in a very hard water area but toilets didn't seem to be a real problem.

[SteamyTea]

8 minutes ago, Gone West said:

with the same low rainfall as your area

Not really rainfall amounts that is the governing factor, more geology.  The whole of the UK gets plenty of rain, just that in some places it cannot be stored is suitable aquifers.

[saveasteading]

2 hours ago, Mulberry View said:

if we should harvest it all,

Yes but....

 

If you are only catching half the roof, then the solution is barrels.

If you can catch all the water without extensive drainage revisions then it becomes more useful because twice the size of tank is only about 30% dearer.

 

For a retrofit I doubt if it is viable commercially, and could probably prove it is not viable sustainably either.

 

Agree with all NickfromWales says.

 

Proof:

I designed and built our own office block with all such considerations in mind. all rainwater collected from the 500m2 roof, through a stilling chamber then to a very big rwh. 

It was sized so that it would catch all the rain from a big downpour. (ie twice the usual recommended size). then overflow to soakaways and a lagoon.

I predicted a 12 year payback, but it was better than that.

Because no rainwater went into the sewers there was a big reduction in rates. PLUS because the sewage charge is based on the amount of water used, that cost was very low too.

From checking the water bill, i appeared that the tank was only empty for perhaps 2 weeks of the summer.

With that in mind the payback looked more like 8 years.

 

However. 

1. the pump broke down and cost a lot to fix

2. No idea of the electric cost for pumping

3. the pump broke down again..

4. It is an office so a high proportion of flushing water compared to potable.

 

At home I have inserted a weir into a gutter to guide most rain to the downpipe with the barrel)

 

On another project where aesthetics were not an issue, I designed a surface rwh using 3 IBCs linked together...capital cost £50.

For  a house 1 would do, but very ugly and bulky.

 

 

Summary: 

Newbuild, designed to suit, and my eagerness to be seen to care.

commercially just about viable

sustainability...yes a good thing in our case.

 

Ugly newbuild with space..use IBC

 

Retrofit? Unlikely to be viable so convert all down pipes to accept barrels, and connect several if you want to collect it all.

If you want, you can divert the overflow to the garden rather than drains.

Catch all the rainwater if possible, and you can get your rates reduced,

 

 

[Gone West]

2 hours ago, SteamyTea said:

Not really rainfall amounts that is the governing factor, more geology.  The whole of the UK gets plenty of rain, just that in some places it cannot be stored is suitable aquifers.

The UK as a whole gets enough rain but in some areas of high population density, low rainfall and unsuitable aquifers, storing surface water is a good idea. Maybe a national grid for water supply, as is discussed every time there is a drought, would be worth doing.

[SteamyTea]

24 minutes ago, Gone West said:

Maybe a national grid for water supply, as is discussed every time there is a drought, would be worth doing.

Or just use less. Charging more usually works.

[Thorfun]

3 hours ago, Mulberry View said:

Any advocates of Rainwater Harvesting on here? I know some see it as questionable from an ROI standpoint, but for us it's not just that we're interested in. The idea of using rainwater to flush the toilets, to reduce limescale (we're in a very hard water area) is of interest. We might also like to use it for the washing machine. But being able to water the garden, specifically the lawn, in a guilt free way is the main driver for us.

 

We would also benefit from some eco-friendly water input as our water consumption data is a little over what was specified in planning (105 litres per person, per day).

 

But what size tank should we look at? We've got about 150sqm of roof space roughly 50/50 over 2 roofs. At the moment, only one roof is designed to go to a Rainwater tank, with the other is going to a normal soakaway. I'm wondering if we should harvest it all, maybe with a larger tank, or perhaps with a second tank? (one close to the house, one for the garden/car washing etc.)

 

Any help is appreciated.

 

we have bought, but yet to fit, our RWH tank (5000l) from rainwaterharvesting.co.uk. we got the gravity fed system so we will have a header tank in the loft for flushing the toilets which means that the pump isn't running every time a loo is flushed but once when the header tank is empty.

 

we also didn't do it for any kind of financial reason and couldn't give 2 hoots about ROI. we want to reduce our reliance and impact on the drinking water supplies and also don't like the idea of sending drinking water to waste down the toilet.

 

if you want to do it then I say go for it. ignore the nay-sayers about ROI and costs etc and just do what you feel is the right thing to do. 😇

[Simon R]

4 hours ago, Mulberry View said:

Any advocates of Rainwater Harvesting on here?

Well, we only got into RWH because of the 19K+ quote to connect to the surface water drain.

Roof size 150m2, our tank is 4,600ltr from which we flush our toilets and run the washing machine. It's just the two of us and we've not run out of water yet. However we are just getting our garden done and I suspect that may change the equation. As insurance all our RWH take-offs all have a mains water option, none off which have been used.

The system we opted for was the Kingspan Klargester, nice tank but very poor implementation of the controls. The pump failed and so has the tank depth sensor. No support from Kingspan and a call out cost of £300, which is more than the new pump cost. If we were to do it again I would get a tank, depth gage and pressure activated pump like the Divertron 1200x (get one with a float intake). A case of keep it simple.

[saveasteading]

2 hours ago, saveasteading said:

Catch all the rainwater if possible

One more thing. Some of the rwh manufacturers include or suggest a 'leaf diverter' which skims 10% of the water away from the surface with leaves etc and dumps it.

This seems like a lot of waste and defeating the object. The same can be achieved by having the rwps go through a grille, or insert a filter in line. My solution was a catch-pit where the silt and leaves were caught, but in real life the muck was insignificant.

 

As SimonR, the backup from the manufacturer was appalling. My supplier has dropped out of the rwh market, fortunately. 

[Chanmenie]

I was advised against it by a guy who worked for a water authority and inspected the things, he said he’d never have one. He’s inspected houses where the cisterns have gone black and stink. 
When you look at the crap and bird shit that gets washed off your roof.

[Simon R]

2 hours ago, Chanmenie said:

When you look at the crap and bird shit that gets washed off your roof.

We had those concerns too. Interestingly when we walked in NZ RWH was the norm for remote buildings, and filtered  was what we drank!

It does require maintenance. We have 'scotchbright' pads in all the drains to filter out the big bits.  The water that comes through pipe is clean and orderless. The washing machine loves the soft water as do all the house plants. It's very important to have a decent tank and keep out all light.

We were somewhat panicked by Mr Harris's comment on RWH, but three years on we're glad we have it.

[Nickfromwales]

Some people choose to pour their hard earned cash into different endeavours, regardless of the economics. Entirely their prerogative.  The heart wants what the heart wants.

If you did a proper paper study, the heart would ( should ) get overruled by the head.

 

Bottom line is, do whatever you wish with your money, but hear, here, the pros / cons / caveats in order to arrive at your own informed decision.

 

My 2 cents is, for the biggest damn tank you can afford, as that’s when ( and IMO ONLY when ) it makes any sense to install RWH. 

[Pocster]

I looked into this . Even have a non return valve in an access chamber installed as requested by the water company specifically for this . ROI was bad . But like others that’s not really the issue . So instead I spent the rain water recovery ear marked money on pv . Amount of water a toilet or washer needs is quite small . A rainwater butt outside fed off the roof will provide enough storage to water the garden . If I had more money I would of installed it as a matter of principle .

[Gone West]

At a Victorian cottage I renovated back in the nineties we discovered a large underground brick and render tank that originally stored rainwater. The rainwater was filtered through a two stage sand filter bed and the water in the tank was crystal clear and had obviously sat there for decades unused. We found the original lead pipe that took the water to the old copper. I cleaned the filter bed and installed a pump and used the water for the garden for many years.

[Chanmenie]

Yes if you go to the added expense of large really efficient filters then it should be ok, but the companies that sell the systems don’t tell you that.

I used to keep Koi carp and the water quality in my pond was very good, but I had a huge expensive filtration system to keep it that way.

[Roundtuit]

48 minutes ago, pocster said:

I would of installed it as a matter of principle .

Each to their own of course, but I don't really get what the principle is?  Is it a perceived environmental benefit?  Don't forget that when you buy your water from your local water supplier, your money is also financing water recycling on a massively more efficient scale, investment in wildlife habitat and biodiversity enhancement, leisure facilities,  investment in renewable energy, community support initiatives...

[Pocster]

11 minutes ago, Roundtuit said:

Each to their own of course, but I don't really get what the principle is?  Is it a perceived environmental benefit?  Don't forget that when you buy your water from your local water supplier, your money is also financing water recycling on a massively more efficient scale, investment in wildlife habitat and biodiversity enhancement, leisure facilities,  investment in renewable energy, community support initiatives...

True . But you could argue the same for using your own generated electricity ( not just carbon saving ) I.e creates jobs / investment etc etc .

My ‘ principle ‘ was to be less dependent on infrastructure; where possible .

[SteamyTea]

4 minutes ago, Roundtuit said:

Each to their own of course, but I don't really get what the principle is?  Is it a perceived environmental benefit?  Don't forget that when you buy your water from your local water supplier, your money is also financing water recycling on a massively more efficient scale, investment in wildlife habitat and biodiversity enhancement, leisure facilities,  investment in renewable energy, community support initiatives...

That is interesting.  I generally agree that it is more efficient to do most things at large scale i.e. I can't get a quarter pounder out of a Dexter, without harming the Dexter.  The thing with water though, well waste water, is out old shared road, house and foul water sewage system.

Cornwall has an annual rainfall of 1100 mm.  So take a roof of 50 m², that is 55 m³ of water, that does not need treating, being treated.  Now the treatment is probably very low cost, but the infrastructure to transport it to the plant, then pump it back to the dog shit strewn beaches, as clean water, is expensive.

The price of each is probably quite hard to disaggregate from the wholes.

[SteamyTea]

9 minutes ago, pocster said:

creates jobs

Oh, my favourite saying.  Along with 'hard earned'.

If I wanted a decent job, I want it to be easy money, less hassle, close to home etc.  Why should every worker have to suffer for a decent living.

A quick way to create jobs is to damage the environment, then employ people to put it right.

Or, take all the people that currently work in the 'unemployment' business, sack them, then reemploy from the ones that have no current job.  Cycle this ever month.  Cut costs and gets rid of unemployment.

(our fixation in the Western World goes back 90 years to the Wall Street Crash and the unemployment that caused, sometimes called The Great Trauma)

Edited April 30, 2022 by SteamyTea

[joe90]

I decided against full RWH fir the build but plan to capture rainwater from the workshop to supplement garden watering using gravity no pumps, simples.

[Chanmenie]

Yes joe I had similar thoughts having decided against feeding toilets and washing machine, I will use a tank to catch the rainwater off the garage and use it for car washing, gardening etc 

[joth]

4 hours ago, Roundtuit said:

Each to their own of course, but I don't really get what the principle is?  Is it a perceived environmental benefit?  Don't forget that when you buy your water from your local water supplier, your money is also financing water recycling on a massively more efficient scale, investment in wildlife habitat and biodiversity enhancement, leisure facilities,  investment in renewable energy, community support initiatives...

It's definitely worth asking the question.

For us (Hertfordshire) the mains water is pumped out of the aquifer which destroys local chalk streams. They dump filtered sewage back into those steams to make up for the abstraction, which further destroys the chalk stream ecosystem.

Reducing demand on mains water by capturing rain will clearly and directly reduce the damage to those streams. Also RWH can reduce the runoff to the city drains which also reduces the load on that infrastructure.

Affinity and Thames water make great noises about how much they do to save the streams, but at the same time the owners are  siphoning off billions of pounds of tax payer subsidised profits via hidden companies in the Bahamas so I have no faith at all that my money handed over to privately owned public infrastructure being good for the local community

 

The economics of RWH never stacked up, but we *very* nearly did it on principal alone. Feargal Sharkey did a talk about it in our local pub and was very persuasive.

In the end aside from cost, the final straws that stopped us were realising it will be empty at the exact times our demand was highest and also when the environmental benefit of it would be highest, and admitting to ourselves we'd not keep on top of the maintenance and we'd end up with mouldy toilets. (Our plumber was very adamant about that being an inevitability) 

 

Still sad we had to cut it from the build.

 

If a whole street or the local school installed it, maybe it could work more efficiently and effectively.

 

Edited April 30, 2022 by joth

[SteamyTea]

So older members may recall that Jeremy Harris made an ozone pump for his drinking water.

If RWH is purely for non drinking, maybe a simple generator pump and some fishtank aeration stones would keep the water sterile enough to stop most problems. May only need a few minutes a day to work enough.

Better than sunbed tubes in my opinion as it delivers the oxidant right to where it is needed.

Edited April 30, 2022 by SteamyTea