Rain Water Harvesting - Vanity Project or Financially Viable?

[noj]

Since we're on a water meter I've been toying with the idea of using rain water for loo flushing and maybe filling the washing machine (in addition to garden watering). It's a tempting idea, but the romance of 'free' water may be greater than the genuine practicalities of pumps, switches, filters, secondary plumbing and not to mention the potential for leaks.

Anyone got any experience of hybrid mains/harvested water and the associated problems that they could share?

We've got the advantage of a great big period cistern (something over 15 cubic m and lined in concrete at some point too) just outside the kitchen that collects rain water from most of the cottage and even in the dry South East that should be sufficient for our needs.

Currently I do use the water for the garden (most of the time) - I just drop a cheap submersible pump down there when required and so this already reduces our metered water requirements and therefore cost savings from a more permanent set-up.

Thanks - any thoughts appreciated.

 

[charlieboy]

And I thought the water tank in my cellar was big!

 

[Flyfisher]

No direct experience, noj, although I entertained thoughts of something similar myself when starting our project but they sort of fizzled away. A pre-existing 15m3 cistern might have focused my mind a bit more!

All I've managed to date is to collect rainwater from an outbuilding roof into three large interconnected barrels. Until this year, these had been sufficient for our meagre garden needs but we've recently undertaken a fair bit of landscaping and (for us) extensive planting for which watering cans filled from the barrels has been insufficient (well, more like hard work actually!) and we've resorted to using a hose pipe. We're on a meter so I was expecting a slightly higher water bill but I received our quarterly bill recently and it was £124 instead of a previously very consistent £60-ish. I'm now thinking of buying a submersible pump for our water barrels and connecting that to the hosepipe instead of the mains tap!

I don't know the likely costs of rain water harvesting for internal domestic uses but imagine there would need to be a reasonable amount of plumbing necessary to divide the two separate water sources - mains and harvested. Not particularly technically difficult but quite possible very disruptive, which may or may not be a big problem depending on the stage of renovations. I imagine there would need to be a level of filtration to prevent the pumps and pipework from silting up over time, plus the need for a pump or pumps as well, for which there would be a running cost, as well as power cuts to consider. However, in our case, the annual savings would likely not exceed £250-ish per year (assuming we stop watering the garden with mains water) so I'd expect the payback period to be many years.

Just some random thoughts really - probably not too helpful. I'd guess there is a lot more info available online.

 

[JoceAndChris]

Hi - we make it work for us - it isn't ideal though. The rain from the roof - which is stored in an underground chamber that sounds similar to yours - is then pumped up into attic tanks and feeds the loos and shower and bath. If we run out of well water ( we aren't are on mains) we are unable to use our washing machine and dishwasher as we chose to plumb those into the well supply.
The rain goes through a bank of particle filters - around 5 filters in total. We installed them ourselves and the cost was around £600. They remove the worst of the mud ( the bottom of to chamber is identical to the bottom of a pond) but the water in the bath and loos is always yellow.
When the water nears the bottom of the chamber ( ie with low rainfall) there is a distinctive smell of mud in the shower.
This problem could be fixed by applying some kind of filter before the rain flows into the chamber but it isn't really very straightforward to fit such a thing.
The dirt and leaves that wash off a large roof is really quite staggering.
As for leaks, it has happened, flooding the attic, it was a disaster but Chris has now fitted a switch that will prevent that overfill from happening again.
All in all, if I could go on mains I would. The rain isn't pleasant to wash in!!

 

[88v8]

1. What's the metered cost per gallon?

2. How much is the projected annual saving?

3. The capital cost of achieving that? The annual running costs?

Costs x 6% investment income is the amount you'd be sacrificing to achieve any saving.
I suspect for anything other than limited garden watering, it would be a waste of time and money.

We were metered at our previous house. I never hesitated to water the garden in dry weather. Sometimes left two sprinklers on overnight. IIRC our largest quarter was >£400, but it's just part of the cost of running the garden. Is the garden somehow unworthy of expenditure?
Using a submersible pump to move whatever water you have around the garden is a good idea, one can get a lot of pump for one's pound.

Ivor

 

[Penners]

If your idea is simply to save money on metered mains water, then you really need to follow through on Ivor's suggested formula. My bet is that you won't see a financial benefit.

I'm also concerned about your idea of having a hybrid mains/rain water domestic system. I suspect there will be a lot of regulatory hurdles involved with this - that is if it's actually permitted at all.

You could perhaps rig up an independent system connected just to the washing machine, at no great cost. However, personally, I think I would just continue to use the stored rainwater for watering the garden and washing the car

 

[Flyfisher]

Good point about regulations Penners, I hadn't thought about that. Now you mention it I recall JoceAndChris once describing how their well water now has to be inspected by the local water authority and they had to have some form of purification system installed. But presumably that's just for drinking water (though I think I'd include dishwashers and showers etc.) and I'd be surprised if there would be a regulatory problem with using rainwater for flushing toilets.

Ivor's point about water being a cost of gardening is a fair one (though I must be a stingy gardener in that case!) and at £400+ per quarter it helps to make a stronger economic case. My general feeling, though, is mains water for inside the house and stored rainwater for outside.

 

[noj]

Technically it's all achievable (including automatic switching back to mains if required - within the regs) but I think the savings would be minor at best and adding in the disaster potential I think it'd just be a vanity project. Obviously there are lots of companies out there selling complete solutions and making wild cost saving claims but in reality it looks like it might save around £100 in metered water/disposal charges and the longevity of the various pumps, valves, switches has to factored in too.

Watering the garden using my cheap submersible pump from Liddl is very cost effective though. This currently needs me to drop it down on a rope and run the extension lead out. At some point a fixed setup with a hard wired pump and an on-demand controller plumbed to a permanent garden tap would probably be cost effective and cover all those little bits of watering can filling that aren't worth the faff of getting the pump out... Economically that probably makes sense only when I need to replace the pump...

But many thanks for your thoughts everyone!

 

[philpjuk100]

I have considered using water from the river at the end of my garden,it could be of use in a few ways,we have "riperian rights" which allow us to moor,fish and extract water (4,400 galls a day).I have looked into putting a heat exchanger for a heat pump in the river.Also considered floating a sort of catermeran with three out of phase paddle wheels on it driving a couple of alternators for my immersion heater.I know undershot wheels are not efficient but the river level varies and I doubt if I would get permission for a dam!.I do use river water for watering the plants at the lower part of the garden via a 12v bilge pump fed from an old lorry battery with a couple of solar panels on top.I could use this supply for flushing the "loos" which are fed from the hot water expansion tank and could be rerouted to their own tank.I do not think that I would use it for the shower as people have been ill after swimming in it!.

 

[Flyfisher]

Lovely spot there Philip - certainly no need for rainwater harvesting!

I do not think that I would use it for the shower as people have been ill after swimming in it!.

From your location I'm guessing that would be the infamous 'Trent Belly', an affliction that often affects users of the white water course at Holme Pierrepont just outside Nottingham. I know this from many years of FF junior using the facilities there. We first went there nearly 15 years ago and kayakers were recommended to drink a can of Coke after using the course to help prevent said affliction. Fortunately, FF junior seems pretty robust in that respect, probably from playing around in ponds and rivers from an early age.

 

[philpjuk100]

Yes we are downstream of there on a "non navigable" part of the trent, although I manage a bit of navigation with my "squirt" jet boat.I have drunk a bit of the trent on a couple of occasions and have found a couple of pints of pedigree a good antidote!.

 

[Penners]

I doubt if I would get permission for a dam!

You'll never know unless you ask! :wink:

 

[Penners]

the infamous 'Trent Belly'... kayakers were recommended to drink a can of Coke after using the course to help prevent said affliction.

Thereby taking advantage of the well-known medicinal benefits of Coca-Cola?! :? :?

 

[MatthewC]

The 13 year old daughter of a friend of mine is an Olympic-capable swimmer who recently tried open water swimming; she says the recommended antidote for that is Coke - I guess that's why I never touch the stuff...

 

[Flyfisher]

Thereby taking advantage of the well-known medicinal benefits of Coca-Cola?! :? :?

I share your scepticism, mainly because FF junior has never apparently suffered from drinking river water despite avoiding this 'remedy' but as Matthew mentions it seems to be a widely held view and I'm sure there are many examples where people have been in open water without any ill effects after drinking a can of Coke, which obviously 'proves' the point :wink:

I'm reminded of fly fishing in Scotland where the ghillies will all have their own recommendations for the best fly for particular rivers and conditions, which means they are the most used flies and therefore catch the most fish and so the reputation of that fly on that river is duly reinforced.

In that spirit, let me offer a sure-fire remedy for the common cold. The next time you catch a cold, place a fresh pea in your right ear. I can pretty much guarantee the cold will have gone within five days. What more proof could anyone want? :wink:

 

[Penners]

:lol: :lol: :lol:

Excellent advice, FF! In the same spirit, may I recommend a grimy greenhouse in your garden as a deterrent against elephants? We have such a greenhouse, and we haven't seen an elephant since... ooooh.... I can't remember when.

 

[noj]

To keep it off-topic: I've always found that drinking far too much the night before is good for a hangover...

 

[steveb]

:lol: :lol: :lol:

Excellent advice, FF! In the same spirit, may I recommend a grimy greenhouse in your garden as a deterrent against elephants? We have such a greenhouse, and we haven't seen an elephant since... ooooh.... I can't remember when.

Aha - I'd never seen an elephant in my garden and often wondered why. Now I know - thanks Penners

 

[philpjuk100]

Whatever became of Fred Drift ?.

 

[Penners]

He would appear to alive and well!