a possible DIY rain-water harvesting system?

timmer3

just starting to research this today, half way through a rennovation of an end-of-terrace house, and wanting to be as 'green' as i can. i've looked at a few systems so far, and from what i can gather to get a 'managed' system with intelligent controls and filters and mains water top-up etc will cost anywhere from €3000 to €10000. watertanksonline.co.uk sell a popular system 'envireau' 3000 litre.
€3k is reasonable i guess and €10k seems excessively expensive, although i'm sure they are all great products. i do understand that water charges will be a big factor and it could soon cost as much as a gas bill or whatever. but still. they say these systems will save 50% on mains water supply. and if you get good quality filters etc you can use the water for showers. but i'm thinking i could still make a reasonable water saving by using completely untreated unfiltered rain water for toilets and garden tap, without any need for pumps or control systems. since the rain-water originates at roof level, why bother letting it fall to the ground only to pump it back up again? why not divert the water from the gutter directly into the attic, and have a large tank there which can supply gravity fed water to cistern and garden taps. the tank could be set up to overflow back down the drainpipe. is it a capacity issue, having such a large amount of water stored in the attic? is it a daft idea? i guess you'd need a strong attic floor. i suppose a 3000 litre tank would weigh 3 tonnes, that's not what you want over your head while you're sleeping i suppose. does anyone know what size tank you would want to make it worthwhile?
i've read other posts about bacteria and algae etc but want to leave that issue to one side for the moment.

timmer3

the more i think about it the more i think it is a daft idea. there is a great advantage to having a massive reservoir under ground, you could get enough rainfall during spring to last you through the summer. and if i did go for the 'DIY' approach i'd have to add in features like mains water top up in case the tank ran dry, and how far do you go down that road before you realise you should have bought a proper system in the first place...
i know this has been asked a few times, but does anyone have a proper rainwater harvesting system? (i.e. more than a barrel on the end of a gutter). what's it like to use? was it expensive?

mickdw

Its not such a daft idea and have thought about it myself. A typical design of house will have the attic higher than the eves so gravity flow to attic isnt really a runner but you could certainy design in a tank at a slightly lower level in a hotpress or where ever.
The hotpress/storage area could be designed to carry alot of weight and so have the tank being supported on blockwork directly.
You would then get your toilet water and outside tap pump free and should be a useful idea. As you said, a simple overflow to surface water system would be needed.
The system would also need to be mains feed to a minimum level to always allow room for rainwater capture.

dh0661

POST #1 is extremely hard to read, please write in paragraphs

thanks

Joey the lips

If you diverted rainwater from the gutters could you not use a standard attic coffin tank withan overflow built in the difference is that the overflow can be piped down the house to the ground to a buried tank used for watering etc. Then you could have an overflow on this for run off when you reach the desired capacity

Thinking of it an attic contains an 80/60 gallon standard coffin tank(i think) putting an addition 60/40 gallon alongside to collect rain water might not add much weight, The 60/40 gallon could become the primary source and the 80/60 gallon could feed it in times of dry weather. The 60/40 could contain a large overflow running direct to the ground and into ground storage. Say another 60/40 gallon tank.

This is a cheap way of doing it but a few things worry me about this.

1. Bird sh1t from the roof. A major contiminant!

2. Dirt from the tiles. Dirt running down the tiles will arrive into the system.

3. All new modern top flush toilets while they conserve water as they are 3/6 ltr they do not respond very well to dirt no matter how small in the water,

4. Lastly will water be precisly metered in household? I am not to sure of the proposed legislation but I imagined it was a standard fee for domestic being proposed, There is no real incentive to save water as you will need to be connected to the mains there for you will need to pay the fee.


The best system i have seen is my neighbours. He has a barrel in his back which collects water from his gutters. about 3 times a day he brings a bucket of water into the house and pours in into the cistern after flushing. Right you might say its like washing with the old vessel bowl it is backwards but i figure this if he does this at least 3 times prob more he is saving 20 liters of water a day. I figure if the water is metered to the point it is read that is one persons water a day!

But again he does not filter the water

timmer3

good point about the attic/eaves level, hadn't twigged that.

city council recently upgraded the water supply to my area (dublin 12) and i'm told it is a meterable tap they have installed on the supply pipe to each house. so i fully expect pay-per-use in the coming years.

just doing up some calculations to try and estimate what volume of storage i would need (i'll use bullet points dh0661, that good enough for you ?? )

• according to met eireann, greater dublin gets <800mm average annual rainfall every year.
• according to this report: "a typical Irish house with a roof area of 75m2 could potentially collect 51m3 of rainwater annually in an area where average rainfall was 1,000 mm".
• using a total laymans calculation, my house has a 33% smaller roof and the rainfall is 20% less, so reduce by approx 50% => 25m3 / 25,000 litres for my roof/area.
• from that same report, apparently an average toilet flushes 11m3 per year (11,000 litres). although with an efficient 3/6 litre cistern, i expect my usage would be more like 5000 litres.
• i like to water my garden in the summer: currently i spend about 15 minutes @ 15 litres/min flow (my mains water rate) after a hot/dry day (average 30 in the year?) => 225 litres x 30 times = 6750 litres.
• washing machine, one wash per week @ 65 litres = 3400 litres.
• total annual use for recycled water: 15150 litres per year (yikes!).
• leaving out the garden watering, monthly domestic requirement is 700 litres. Mean monthly rainfall is surprisingly consistent during the year for Dublin airport, ranging only from 50-75mm. assuming a relatively even rainfall, at 2000 litres per month, that leaves me with a monthly surplus of 1300 litres on average for the garden.
• with a garden watering requirement of 6750 for april-september (6 months) that is an extra 1000 litres per month for the garden, which is still within average monthly supply.
• this gives me some indication for what size tank i would go for. say i went for a 2700 litre tank @ £2000 cost (including pump + filter), assuming it was full at the start of summer, and worst case a completely dry month (this is ireland after all, and global warming will not reduce average rainfall, just make it more extreme), that would give me 700 litres for domestic leaving 2000 litres for the garden, which would be enough to drench the garden about 10 times during that dry month. not bad?
• for an extra €1000 i think it is probably worth getting a more high-tech filtering system that links in with the mains water supply, giving cleaner water for washing machines etc. such as the envireau 3000 litre. this has some useful gadgets like an electronic depth probe and a display panel with water depth and fault indication.

seems like a runner to me. only thing is, my house has no access for diggers, so i'd have to pick axe a 1.7m deep hole. still, i think the whole thing sounds like a good idea.

Graaaaa

I agree that an underground tank is the only way to go - it would be difficult to develop a system that fills the attic tank from the gutters as it would fill only when it rains and the mains would have filled the tank already.
A friend of mine used the downpipe filter and tank from these guys:
http://www.hiberniaeth.com/html/RainSystems.htm
He's very meticulous and would have researched well before deciding. So far he's happy, can't be more technical about it's performance I'm afraid.

One question - if you can't get a digger out the back, how will you get the tank through? Crane over the rooftops? Maybe some of the GRP tank suppliers provide sets of smaller interconnected tanks? These might be small enough to fit through the front door and could save you digging to deep too - be very careful of ground collapse below 4ft - at 1.7m the pressure would suffocate you in no time and for stability you might have to dig one big crater!

timmer3

thanks a lot for the tip. i've sent them an email asking for some specifications on the 'diamant eco plus' system. i'll let you know if i go with their system and how it performs. i'm glad to find a local supplier, it seems like ireland is slow to catch on to rainwater harvesting (which is surprising). although i'm sure it won't be long, there's nothing like a hefty tax to shift a national mentality - remember plastic bags?

CJhaughey

You can get micro diggers now, that will fit through a domestic doorway, a lot easier than trying to manually dig a 4m3 hole!

Hagar

I pay less than €1 per day in water charges in France, even if you paid twice or three tomes that you will never recover any money spent on water saving schemes.

timmer3

Hagar wrote: »

I pay less than €1 per day in water charges in France, even if you paid twice or three tomes that you will never recover any money spent on water saving schemes.

with the greatest respect, that is a nonsense statement at best.
so we might as well P*** away as much water as we like and water our gardens like an oasis? it's not just about saving money, it's about being responsible with a limited resource. although ireland has plenty of rainwater there is a very limited supply of drinking water. indeed, most rainwater in ireland flows through polluted drains and then pollutes the sea as a result (carrying dog faeces, e-coli, colliform etc), several beaches in ireland (and dublin) lost their blue flags last summer as a result of the rains and associated pollution from the drains. granted this is partly due to road drains but if household rains were collected it would significantly reduce sea pollution.
ireland's water treatment facilities are over-burdened and in several recent cases this has led to contaminated mains water supply. we have rising population density in this country and and an increasingly extreme climate, with more likely occurrences of drought. in ten years time i will have no sympathy for you when you have to wash your car with a single bucket of water (which might only permitted on one day in the week). granted this is not australia where such rules apply, and never will be, but i see absolutely no merit in wallowing in (and encouraging) the culture of waste in this country.
if water charges are introduced at €350 per year then the payback will be slow (but in my view still extremely worthwhile for its environmental benefit). but if it ever gets as expensive as €1000 per year, which is very possible, then it would have to be metered and charged by usage. If you reduced usage by 50% with a rainwater harvesting system then that would reduce costs to €500 per year, thereby giving you a payback of 5 years for a €2500 system, not to mention your positive contribution to the environment and all the other associated benefits of rainwater harvesting. beyond the initial payback you are then saving a lot of money every year.

timmer3

CJhaughey wrote: »

You can get micro diggers now, that will fit through a domestic doorway, a lot easier than trying to manually dig a 4m3 hole!

alright! i didn't know such things existed. i can just imagine driving a digger through my house thanks for the info.

timmer3

Graaaaa wrote: »

One question - if you can't get a digger out the back, how will you get the tank through? Crane over the rooftops? Maybe some of the GRP tank suppliers provide sets of smaller interconnected tanks? These might be small enough to fit through the front door and could save you digging to deep too - be very careful of ground collapse below 4ft - at 1.7m the pressure would suffocate you in no time and for stability you might have to dig one big crater!

my house is end of terrace with only pedestrian access. it does have side access so if the tank(s) weren't too heavy i could get a few lads to help lift over the front gate and around the back of the house. mini digger sounds like a good plan. i could possibly install the tank in the front garden which they might be able to drop in by crane but there are overhead wires everywhere, i think i would try to go with a system i could move in by hand. i looked at the tanks on that web site you mentioned and one model splits in half and is designed to fit through a door alright. the only thing then is they say the seals are 'estimated by a lab' to last 25 years. and then presumably the system could start to get contaminated with no way of knowing if or how much.
i was thinking about the size of the excavation alright, it would have to be very carefully dug.

Hagar

timmer3 wrote: »

with the greatest respect, that is a nonsense statement at best.
so we might as well P*** away as much water as we like and water our gardens like an oasis? it's not just about saving money, it's about being responsible with a limited resource. although ireland has plenty of rainwater there is a very limited supply of drinking water. indeed, most rainwater in ireland flows through polluted drains and then pollutes the sea as a result (carrying dog faeces, e-coli, colliform etc), several beaches in ireland (and dublin) lost their blue flags last summer as a result of the rains and associated pollution from the drains. granted this is partly due to road drains but if household rains were collected it would significantly reduce sea pollution.
ireland's water treatment facilities are over-burdened and in several recent cases this has led to contaminated mains water supply. we have rising population density in this country and and an increasingly extreme climate, with more likely occurrences of drought. in ten years time i will have no sympathy for you when you have to wash your car with a single bucket of water (which might only permitted on one day in the week). granted this is not australia where such rules apply, and never will be, but i see absolutely no merit in wallowing in (and encouraging) the culture of waste in this country.
if water charges are introduced at €350 per year then the payback will be slow (but in my view still extremely worthwhile for its environmental benefit). but if it ever gets as expensive as €1000 per year, which is very possible, then it would have to be metered and charged by usage. If you reduced usage by 50% with a rainwater harvesting system then that would reduce costs to €500 per year, thereby giving you a payback of 5 years for a €2500 system, not to mention your positive contribution to the environment and all the other associated benefits of rainwater harvesting. beyond the initial payback you are then saving a lot of money every year.

The payback will be non existant at €350 a year. If you could service all your water needs, which is impossible - drinking water must be bought etc - from a €3500 unit you would theoretically break even in 10 years. In practice you have to factor in paying for your "drinking" water from the council, running and maintenance costs and the ineveitable inefficiencies caused by unnecessary waste of "drinking" water, possibly droughts etc and you will probably push the payback time another couple of years at which time the whole shooting match is probably ready to be ripped out and replaced.

Where's the environmental benefit in the manufacture and distribution followed by the scrapping of ineffective systems being peddled by get rich quick merchants cashing in on the green bandwagon?

Your living in a green dream, not everything we'd like to do is possible.

timmer3

Hagar wrote: »

The payback will be non existant at €350 a year. If you could service all your water needs, which is impossible - drinking water must be bought etc - from a €3500 unit you would theoretically break even in 10 years. In practice you have to factor in paying for your "drinking" water from the council, running and maintenance costs and the ineveitable inefficiencies caused by unnecessary waste of "drinking" water, possibly droughts etc and you will probably push the payback time another couple of years at which time the whole shooting match is probably ready to be ripped out and replaced.

Where's the environmental benefit in the manufacture and distribution followed by the scrapping of ineffective systems being peddled by get rich quick merchants cashing in on the green bandwagon?

Your living in a green dream, not everything we'd like to do is possible.

sorry but nonsense again. nobody said you could service all your water needs, although with a more advanced filter you could purify the water cleaner than supplied by the local authority, so you could actually. but practically speaking, 50% is the accepted saving if you use rainwater harvesting. the €350 per year *is* the only cost you need to factor in for your drinking water. the investment in rainwater harvesting will be a direct payback depending on the water charges. it's just a tank with water in it. the filter is easy to clean, there are no maintenance or running costs. a water pump uses a tiny amount of electricity. when a drought comes (with the associated water shortages) i will be the one with neighbours queuing up for buckets of water to flush their toilets and shower since i will have a massive reservoir (don't worry i won't lend you any). why would the system ever need to be ripped out? it's a plastic tank that will never degrade. a pump might have a life-span of 20 years, but that only costs a few quid to replace anyway.
fair enough it costs energy to manufacture and transport a large plastic tank. in my uneducated view that would easily be recouped by the massive saving on the treatment of the water i would otherwise have to get treated by the local authority. say over 10 years, 150,000 litres of water used in my house would not be required. now that costs money, and huge amounts of chemicals, so i'm sorry but your manufacturing/energy point does not hold water (sorry, couldn't resist).
i don't understand why people are so negative and pessimistic about green issues. i don't live in any dream, i am adopting a very practical approach to insulating and rennovating my house and of course i make compromises where there is no great advantage in adopting a particular green technology. for example i am not getting solar panels because the house is north facing and i have very little use for stored hot water anyway. if i had a field though i would put in a wind turbine.

of course there is a green bandwagon but one of the most useful things i have found from the boards.ie community is the expertise and experience of other users who have discussed the advantages and disadvantages of those technologies that are proven, and where unproven, at least there is dialogue to discuss their potential merits. you obviously aren't an early adopter.

timmer3

also, you said even if the water charges were €3 per day you could never get any back. clearly there would be a short payback in this case.

timmer3

ok i didn't see that you highlighted the sentence in my post and were referring to the €350 annual charges. fair point at €350 there is very little in the financial argument for rainwater harvesting. but who is to say it will be that low? and will stay that low?
(didn't think you were allowed highlight quotes but since you're a mod i'm sure you'd know).

Graaaaa

In the UK, if your water use is low enough, you can become a 'net contributor' to the sustainability of the potable water supply and the water companies (private, not councils) will actually refund your standing charges.

Bet that'll never EVER happen with the muppets running this country though.

As for drinking water costs - you can get 4 x litre bottles in Aldi/Lidl for the same price as 250ml of 'fashionable' water in a corner shop. In France I've seen 5 litre drums in supermarkets for next to nothing. so assuming we can find an economical source of drinking water, and cisterns, showers and washing machines are filled by rainwater, then the only water use from the mains will be for the kitchen sink for food preparation.

Another benefit - clothes washed in clean soft rainwater require less detergent, come out cleaner, whiter and softer than in treated water (hard or soft) and last longer because the fibres remain in better condition.

So savings in the long run are not simply direct.

A word of warning about using your front garden - be careful about collapse of walls/footpaths where you might be liable. Don't know if the council have any say as to what goes on in the front garden if it can be considered construction, but it's likely your watermain, gasmain and possibly the common foul drain (if your end of terrace, or corner) all run through your front garden.

timmer3

Graaaaa wrote: »

In the UK, if your water use is low enough, you can become a 'net contributor' to the sustainability of the potable water supply and the water companies (private, not councils) will actually refund your standing charges.

Bet that'll never EVER happen with the muppets running this country though.

As for drinking water costs - you can get 4 x litre bottles in Aldi/Lidl for the same price as 250ml of 'fashionable' water in a corner shop. In France I've seen 5 litre drums in supermarkets for next to nothing. so assuming we can find an economical source of drinking water, and cisterns, showers and washing machines are filled by rainwater, then the only water use from the mains will be for the kitchen sink for food preparation.

Another benefit - clothes washed in clean soft rainwater require less detergent, come out cleaner, whiter and softer than in treated water (hard or soft) and last longer because the fibres remain in better condition.

So savings in the long run are not simply direct.

A word of warning about using your front garden - be careful about collapse of walls/footpaths where you might be liable. Don't know if the council have any say as to what goes on in the front garden if it can be considered construction, but it's likely your watermain, gasmain and possibly the common foul drain (if your end of terrace, or corner) all run through your front garden.

thanks for the info, very interesting about the UK system. you never know, we might get a new government some day. my gas and water main are through the front garden, thanks for the warning here, definitely more suitable to use the back. thanks.

Joey the lips

Folks thought of a very simple harvesting system last night. Whats to stop you burying 2 no 80 Gallon tanks in tyhe yard allowing the water flow into one filter it into the other and using a sump pump flow switch let the pump send it back to your attic tank. If there is no call for it in the attic let it flow off through the overflow back into the drain. I reckon it would involve about 500 euro in parts and simular in Labour. The only on going cost is filtration but if its not been used for drinking water no real heavy filtration will be required.

The problem with this system is its pointless if you are charged a fixed charge instead of a usuage charge.

PeteHeat

Hi,

PM sent, I would appreciate your feedback.

Apology, P.M. Sent to timmer3

.

Hairy mellon

Major costs for rainwater recycling is retro fit of plumbing internally to get second water supply system to cisterns etc. fresh water supply for drinking must be separate from grey or recycled water for flushing. In a new hoise the cost for this is negligible, so its a no brainer to future proof.

Second main cost is tank. Typically for a 3-4 bed home youre looking at a 3000l+ tank with submersible pump- this gives minimum 21 day reserve (there are plenty of online calculators that will do this in more detail)

There is a body of opinion on this that suggests go much smaller on reserve period. Safer for bacteria growth etc and tank/costs a lot lower. A bit like your mate with the water but out back.

Logically rainwater harvesting is absolutely the way to go. It kills two birds with one stone- it acts as a local attenuating system for storm events thus significantly reducing stress on an existing undercapacity drainage system, while reducing the need for treated water from reservoirs by up to 50% per household.

The only way to promote this effectively is to tax water to push homeowners into action- this is happening atm. The whole payback thing will pretty soon make sense, however costs from supliers of systems may well increase proportionately (subsidies or tax frequently has unintended consequence of distorting market)