Harvesting Rainwater

20-10-2013 10:04am

By the way 2 cubic meters of water weighs 2 metric tons!
This extra weight will be spread across a few joists. Better check that they can take the additional load :eek:

Dtp1979 · 20-10-2013 1:19pm

2011 wrote: »

By the way 2 cubic meters of water weighs 2 metric tons!
This extra weight will be spread across a few joists. Better check that they can take the additional load :eek:

I'm not putting 2 cubic metres in the attic. I'm using my existing attic tanks, putting the 2 IBC outside and pumping up to the attic. 2000 litres of water is alot of showers and flushing toilets

20-10-2013 1:50pm

Dtp1979 wrote: »

I'm not putting 2 cubic metres in the attic. I'm using my existing attic tanks, putting the 2 IBC outside and pumping up to the attic. 2000 litres of water is alot of showers and flushing toilets

Fair enough.
Where will you locate the pump and filtration equipment?

Dtp1979 · 20-10-2013 3:12pm

2011 wrote: »

Fair enough.
Where will you locate the pump and filtration equipment?

Beside the tanks outside. They will be insulated and weatherproofed in one unit

yellatdave · 20-10-2013 3:29pm

2011 wrote: »

This will mean that you will have to pay the (knowing this country over inflated) water meter standing charge.

So you will need:
1) Tank(s) outside
2) Tank(s) in the attic
3) Buy, run and maintain a pump
4) Buy, run and maintain filtration system.

All this so that you can store about €4 of water???

Somehow I don't think that this will catch on

2000 litres = 1 cubic meter
Dublin County Council seem to be suggesting that a cubic meter of water will cost in the region of €2

Link:
http://www.dublincity.ie/Business/WaterCharges/pages/waterchargescalculate.aspx

2000 litres = 2 cubic metres, but based on the above cost, I'm coming in at €438 annually for a 4-person household:

Usage of approx 150 litres per person per day (source: http://www.waterwise.org.uk) for a 4-person household is 219,000lt per year, or 219 cubic metres @ €2 per cubic metre

While the €2 per cubic metre quoted is a business rate, it's broadly in line with UK domestic rates (Anglian water charge €1.80 approx per cubic metre), so probably pretty close to what its going to be.

Reckon I need:
1 x Pre-Tank Filter (€25)
2 x 1089lt potable water tanks (€1000)
1 x submersible pump with float switch (€150)
1 x MDPE 10mt flexible pipe (€25)
1 x 2-filter system (€165)
1 x control box (€40)

Rough costs:
Initial Set-up = €1,405
Annual running cost (filter cartridge replacements & electricity) = €65

Based on above, payback period in less than 3.5 years for 100% rainwater use. Reckon I'll be using 70% rainwater, thereby giving a payback period of roughly 5 years (if my maths are right!!)

yellatdave · 20-10-2013 3:34pm

2011 wrote: »

Fair enough.
Where will you locate the pump and filtration equipment?

Dtp1979 wrote: »

Beside the tanks outside. They will be insulated and weatherproofed in one unit

Very similar set-up, but with submersible pump. Float switch will cut off rainwater-feed when tanks are low & control box will then switch to mains-fed.

Would love to use IBC's like Dtp1979 to really cut down cost, but unfortunately need long narrow tanks to fit in limited space.

20-10-2013 3:38pm

Dtp1979 wrote: »

Beside the tanks outside. They will be insulated and weatherproofed in one unit

So the plan is:

1) Rain will fill the outside tanks.

2) This water will be pumped from the outside tanks to the attic tanks with an electric pump.

3) There will be some sort of inline filtration system between both tank systems (located outside).

4) If the outside tanks run dry due to lack of rain or otherwise the mains water will be used to top up the attic tanks.

5) There will be some form of level control on the outside tanks to ensure that the transfer pump does not dry run. This could be achieved easily & cheaply with a float switch.

Is that roughly the plan?
Please correct me if I am wrong.

Does the pump go upstream or down stream of the filtration system?
Have you a filtration system or pump in mind?
Do you intend on producing potable water?

20-10-2013 3:47pm

yellatdave wrote: »

2000 litres = 2 cubic metres, but based on the above cost, I'm coming in at €438 annually for a 4-person household:

Usage of approx 150 litres per person per day (source: http://www.waterwise.org.uk) for a 4-person household is 219,000lt per year, or 219 cubic metres @ €2 per cubic metre

While the €2 per cubic metre quoted is a business rate, it's broadly in line with UK domestic rates (Anglian water charge €1.80 approx per cubic metre), so probably pretty close to what its going to be.

Reckon I need:
1 x Pre-Tank Filter (€25)
2 x 1089lt potable water tanks (€1000)
1 x submersible pump with float switch (€150)
1 x MDPE 10mt flexible pipe (€25)
1 x 2-filter system (€165)
1 x control box (€40)

Rough costs:
Initial Set-up = €1,405
Annual running cost (filter cartridge replacements & electricity) = €65

Based on above, payback period in less than 3.5 years for 100% rainwater use. Reckon I'll be using 70% rainwater, thereby giving a payback period of roughly 5 years (if my maths are right!!)

You will need to consider:

1) Installation charge

2) The cost for pumping 219 metric tons of water from your garden to your attic (5m) per year? Is see that you have only allowed €65 for this including replacement filters. Seems a little low to me, have you done a calculation to back this up?

3) Maintenance costs. See above.

4) Sometimes it simply does not rain. Your calculation assumes that you will always have enough rain water.

5) What size is your roof area? Do you plan to collect all of the rain water from all of your roof? i.e. front & back of your home. Do you think you have enough roof area that you can collect 219,000 per year?

6) Do you have a 4 person household and therefore feel that you would consume the average amount of water for a 4 person household? I ask this because that is what this calculation is based on.

yellatdave · 20-10-2013 3:56pm

2011 wrote: »

So the plan is:

1) Rain will fill the outside tanks.

2) This water will be pumped from the outside tanks to the attic tanks with an electric pump.

3) There will be some sort of inline filtration system between both tank systems (located outside).

4) If the outside tanks run dry due to lack of rain or otherwise the mains water will be used to top up the attic tanks.

5) There will be some form of level control on the outside tanks to ensure that the transfer pump does not dry run. This could be achieved easily & cheaply with a float switch.

Is that roughly the plan?
Please correct me if I am wrong.

Does the pump go upstream or down stream of the filtration system?
Have you a filtration system or pump in mind?
Do you intend on producing potable water?

That's pretty much it. But step 1 will have a pre-tank filter on the downpipe, so no major debris enters the tank to trouble the pump.

Costs of filtration system & pumps were based on quick search of readily-available ones found on ebay/B&Q sites, but haven't settled on any particular one yet.

Still haven't decided on producing potable water. UV systems are pricy, but then again I'd be able to use 100% rainwater.

yellatdave · 20-10-2013 4:19pm

2011 wrote: »

You will need to consider:

1) Installation charge

2) The cost for pumping 219 metric tons of water from your garden to your attic (5m) per year? Is see that you have only allowed €65 for this including replacement filters. Seems a little low to me, have you done a calculation to back this up?

3) Maintenance costs. See above.

4) Sometimes it simply does not rain. Your calculation assumes that you will always have enough rain water.

5) What size is your roof area? Do you plan to collect all of the rain water from all of your roof? i.e. front & back of your home. Do you think you have enough roof area that you can collect 219,000 per year?

6) Do you have a 4 person household and therefore feel that you would consume the average amount of water for a 4 person household? I ask this because that is what this calculation is based on.

(1) Lucky to have an electrician uncle to give me a hand (who set up a similar system years ago).

(2) Replacement filters once a year @ €30. You're right, electricity was a bit low. Based on a 250watt pump running 3 hours a day = €60 annually

(4) That's why I'll have large storage capacity & a mains water back-up.

(5) Hope so! Based on observations of a few hours to fill my 500lt water butt in heavy rain while only using part of the roof catchment area, shouldn't see it as a problem. Was thinking of blocking-off the top of the other downpipe (not used for the system) to increase flow to the tanks, but unsure what weight stress this may pose to the guttering.

(6) Yep, a 4-person household.

20-10-2013 4:38pm

OK, just for the crack I did a very, very rough calculation of the electrical running cost per annum (that ignores all sorts of losses).

Work done to lift 219,000 litres of water to a hight of 5m = 219,000 x 9.81 x 5 = 10,741,950 Joules

(ignoring all losses frictional etc..).

Using a submersible pump such as this SCP5000

Assuming an output of 200W (taking into account pump losses) it will take = 150 hours to pump 219,000 litres of water to a hight of 5m.

Running this 220W pump for 1 hour will consume 0.22 units of electricity.

Therfore running this pump non stop for 150 hours will use 33 units of electricity.

At say €0.17 per unit this equates to a total cost of €5.61

Far less than I expected to be honest. Perhaps I have missed something due to over indulging last night

:)

This assumes that the pump is running constantly, stopping and starting a pump will mean that it will consuming more electricity.

20-10-2013 4:49pm

yellatdave wrote: »

(1) Lucky to have an electrician uncle to give me a hand (who set up a similar system years ago).

Interesting, I would love to see this.

You're right, electricity was a bit low. Based on a 250watt pump running 3 hours a day = €60 annually

Perhaps your electricity allowance is more accurate that I initially thought.

The pump shown in my link above will transfer up to 15,000 litres in 3 hours, on that basis I don't think your pump will need to run for very long (as my pump is a similar size to yours). Although you can expect this figure to reduce due to the 5m head.

Remember 219,000 litres per year is only 600 litres per day (on average).

yellatdave · 20-10-2013 4:51pm

Knew they were efficient, but not that good!

Good pumps, will definitely check out.

yellatdave · 20-10-2013 4:53pm

2011 wrote: »

Interesting, I would love to see this.

More than welcome when up & running.

20-10-2013 5:02pm

yellatdave wrote: »

Knew they were efficient, but not that good!
Good pumps, will definitely check out.

Please don't take my very rough calculation as gospel. In the mist of a hangover I just randomly knocked of 20W from the pump input and gave it as an output to make some allowance for losses

Dtp1979 · 20-10-2013 6:30pm

yellatdave wrote: »

2000 litres = 2 cubic metres, but based on the above cost, I'm coming in at €438 annually for a 4-person household:

Usage of approx 150 litres per person per day (source: http://www.waterwise.org.uk) for a 4-person household is 219,000lt per year, or 219 cubic metres @ €2 per cubic metre

While the €2 per cubic metre quoted is a business rate, it's broadly in line with UK domestic rates (Anglian water charge €1.80 approx per cubic metre), so probably pretty close to what its going to be.

Reckon I need:
1 x Pre-Tank Filter (€25)
2 x 1089lt potable water tanks (€1000)
1 x submersible pump with float switch (€150)
1 x MDPE 10mt flexible pipe (€25)
1 x 2-filter system (€165)
1 x control box (€40)

Rough costs:
Initial Set-up = €1,405
Annual running cost (filter cartridge replacements & electricity) = €65

Based on above, payback period in less than 3.5 years for 100% rainwater use. Reckon I'll be using 70% rainwater, thereby giving a payback period of roughly 5 years (if my maths are right!!)

Would an IBC tank not do for the potable water?

yellatdave · 20-10-2013 7:33pm

IBC's would be ideal (& much cheaper), but unfortunately I don't have the space for them. My garden is long & narrow, so need something to fit snuggly along one wall.

Dtp1979 · 20-10-2013 8:13pm

yellatdave wrote: »

IBC's would be ideal (& much cheaper), but unfortunately I don't have the space for them. My garden is long & narrow, so need something to fit snuggly along one wall.

That's a pity. 120 for 2 IBC tanks. Maybe you could consider burying the tanks?

yellatdave · 20-10-2013 9:22pm

Good idea! But having dug holes in my garden before, once down more than 2 feet it becomes extremely difficult. With IBC's more than a meter high, don't fancy the idea of digging a few holes that deep. Although nothing better than nearly €900 saving to get the shovel out! :rolleyes:

yellatdave · 21-10-2013 9:46am

Dtp1979 wrote: »

Would an IBC tank not do for the potable water?

Forgot to mention 2011's point on algae growth. Algae need sunlight, so you'll have that problem if using clear/translucent tanks like IBC's. Paint the plastic a dark colour or cover the tanks with a blackout material to avoid.

Dtp1979 · 21-10-2013 12:52pm

yellatdave wrote: »

Forgot to mention 2011's point on algae growth. Algae need sunlight, so you'll have that problem if using clear/translucent tanks like IBC's. Paint the plastic a dark colour or cover the tanks with a blackout material to avoid.

Mine would be in total darkness because I'd have them insulated and weatherproofed

wicklow_hills · 28-10-2013 8:45pm

there's a lot more to this rainwater harvesting business that you've considered
if you want it for anything other than watering the garden and cleaning the car

the big issue is safe water storage

there's a company in Newtown that are experts in this area: http://www.rainsafewater.com/

Annasopra · 28-10-2013 9:15pm

Moved from Greystones/Charlesland forum to Sustainability and environmental issues

Crazy Eye · 30-10-2013 7:36pm

wicklow_hills wrote: »

there's a lot more to this rainwater harvesting business that you've considered
if you want it for anything other than watering the garden and cleaning the car

the big issue is safe water storage

there's a company in Newtown that are experts in this area: http://www.rainsafewater.com/

over 2000 euro for that . about 200 euro worth of parts off of ebay and you would make it yourself with some diy skills . very handy for times like this when dublin council are completely shutting off mains water to the capital from 8pm each night .

zagmund · 31-10-2013 12:43am

We had a similar system put in recently when the house was undergoing a complete refurb. Here's a few observations - the pump to bring water from the storage on the ground floor to the attic isn't terribly efficient, so running costs on that are higher than computed above. Basically, every time you flush the loo and use up a couple of litres the pump comes on for 10-15 seconds and goes off again. So, it's a series of small volume lifts over time rather than one big one. If I could get my DIY hat one one of these days I could possibly tweak it a little so that it waits for a greater drop in tank level before doing a lift and then lifts more.

The biggest user of electricity that I can find is the valve that sits between the harvest feed and the mains feed. For some (possibly legitimate/possibly doubtful) reason it's normally open and needs to be powered to be closed. Since the normal state is closed (because we have harvest water and need to close the valve to keep the mains shut off) it is using power 24 hours a day for most of the year. It's not a huge amount. I don't have the figures to hand for the running cost. A manual valve would do the job just as well and since it's only supplying the loos, a situation where we forget to open the valve (to allow mains water) isn't going to result in anything too bad. Feeding a dishwasher or other system could have more problems with a manual valve.

I think we have something like a 900l tank outside and whatever a normal domestic attic tank is inside. Over this Summer we ran dry (and so switched to mains) for maybe 10-14 days. Possibly a little more, but not much. This would have been for toilets and almost no garden watering - this year wasn't a good year for the garden.

We installed the system as a degree of future proofing - the payback may be long, it may be short. One thing is for sure - when the water charges come in we will be saving money (even if only a little) every time we flush the loo. Forever. I've lived in Ireland long enough to know that charges only ever go in one direction.

z

ted1 · 01-11-2013 2:59pm

2011 wrote: »

Unfortunately untreated/filtered rain water is good for watering the garden and little else.

Algae in the rain water will cause it to turn yellow with a green slime forming surface quite rapidly.

This may interest you:

http://rainwaterharvestingsystemsireland.town.ie/

A true rain water harvesting system looks after that with Uv treatment and filters.
My brother has a 2500 litre tank under his patio which treats the water then pumps it up to a tank in the attic fir use in non drinking use

Crazy Eye · 01-11-2013 6:01pm

ted1 wrote: »

A true rain water harvesting system looks after that with Uv treatment and filters.
My brother has a 2500 litre tank under his patio which treats the water then pumps it up to a tank in the attic fir use in non drinking use

any photos of the tank and system ?
how many in the house ? you wouldnt be too long getting thru 2500l of water in longer dry spells of weather though .

Dtp1979 · 01-11-2013 6:54pm

ted1 wrote: »

A true rain water harvesting system looks after that with Uv treatment and filters.
My brother has a 2500 litre tank under his patio which treats the water then pumps it up to a tank in the attic fir use in non drinking use

Does he use it for showering too?

ted1 · 01-11-2013 10:03pm

Dtp1979 wrote: »

Does he use it for showering too?

I'll check with him. It's actually a 3000litre, here's a blog that was done when he was doing the house up.

http://www.jharchitecture.ie/category/south-dublin-ext-refurb/

Crazy Eye · 01-11-2013 11:01pm

ted1 wrote: »

I'll check with him. It's actually a 3000litre, here's a blog that was done when he was doing the house up.

http://www.jharchitecture.ie/category/south-dublin-ext-refurb/

nice project there .can you find out who supplied that underground tank please ? i think its either a uk or german made tank but would like to know where he got it from here in ireland .

Harvesting Rainwater

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