Rainwater Harvester

Masterhalifax · 15 June 2018 at 10:31AM

Morning All,

I have a rainwater harvester system that I am struggling with.....

The system is plumbed in to the whole water system apart from the kitchen cold tap, meaning it will produce water to all outlets, taps, showers, cisterns, ect. I would presume that the system would only supply to cistern, external taps, shower at a push...

So my thoughts are water in my calculations doesn’t appear that expensive, approx 1pence per litre. I was going to re route this system to only provide water for the garden and swimming pool top up. However will it cost more in electric to pump the water through the taps than actually the cost of mains water?

Your thoughts?

jk0 · 15 June 2018 at 12:25PM

Is this a home made contraption? Sounds odd to me to have rainwater for everything other than the kitchen sink.

For garden watering I have two water butts raised on timber frames in my garage, connected to downspouts with diverters. One is for filling a watering can, and the other is connected to a Hozelock water timer, and a drip feed system. This comes on for about 5 mins every evening, so sends about 15 litres into my pots. Thus with a 210 litre butt, it can work for two weeks without rain.

The only electricity required is two Duracell C cells about every 5 years. There is no pump needed at all, as I store the water at height.

Masterhalifax · 15 June 2018 at 1:34PM

Hey, the system is a proper rainwater harvesting system and yes I thought it odd to run it all through to such much of the house.

I have a water butt too. However was going to utilise the harvesting system as it would be cheaper to have it just divert to an external tap rather than re plumb the house to where I would like the harvested water to go.

Suppose the question is how much electric would the water pump use vs the water price from a tap?

A_Nice_Englishman · 15 June 2018 at 1:42PM

As long as the harvested rainwater is stored higher than where you want to use it you won't need a pump.

I'm having difficulty visualising your system to be honest. Did you install it, or inherit it from a previous owner?

martinthebandit · 15 June 2018 at 1:53PM

A_Nice_Englishman wrote: »

As long as the harvested rainwater is stored higher than where you want to use it you won't need a pump.

I'm having difficulty visualising your system to be honest. Did you install it, or inherit it from a previous owner?

Most of them have underground tanks with a submersible pump, if they last more than 30 years your in profit apparently (sooner if water prices continue to rise)

A_Nice_Englishman · 15 June 2018 at 1:56PM

Let's do the sums. Taking this pump as a random example, it pumps 2500l an hour and uses 800w so 0.8kWh (0.8 units) an hour.If a unit costs about 12p that's about 0.004p per litre.

Obviously you have to factor in the cost of the pump, installation, changing your internal plumbing and the cost of the mains water you'll use for washing, flushing etc.

https://www.rainwaterharvesting.co.uk/download/content/download-brochures-and-manuals/hydroforce-pump-brochure.pdf

Masterhalifax · 15 June 2018 at 1:57PM

It!!!8217;s a large tank below ground, all guttering runs in to the tank, sealed unit. Submersible pump pumps water back to the house via a control unit and filter somewhere in the line. Is an Envireau System.

A_Nice_Englishman · 15 June 2018 at 1:58PM

martinthebandit wrote: »

Most of them have underground tanks with a submersible pump, if they last more than 30 years your in profit apparently (sooner if water prices continue to rise)

Thanks, I didn't realise that.

Masterhalifax · 15 June 2018 at 2:45PM

Thanks for the calculation and didn!!!8217;t realise it would be that cheap to run the pump.

So my options are;

1. Have a plumber re route the system to the items I would ideally want, toilet cisterns, outside taps - which maybe costly.
2. Have a plumber just re route the system for an external tap that I can use for garden and pool - less costly, however it then would become an over engineered water butt!
3. Not use it and forget about it - which seems a waste.

bxboards · 15 June 2018 at 3:10PM

Isn't that just a fancy name for a bucket?

edwink · 15 June 2018 at 3:51PM

We have a rainwater harvesting system installed just for our toilet flushing. Our set up sounds like it is so much simpler than yours as does not feed the taps etc.. and our bath and shower water goes in to the tanks as well. If you are on a water meter using rainwater for loo flushing will obviously save you money but the amount will depend on how many times you flush your loo per day and also how many are living at the property with you. Where we are our sewage is charged on 90% of our water consumption. So for example if we use 100 litres of water we are billed for 90 litres of sewage.

Maybe worth checking with your water company if you are on a meter to find out how your water and sewage are billed percentage wise.

Can not really say how much this system has saved us over the years water bill wise because we get a huge discount on our sewage costs for having a soak-a-way. Also, most of the electric for running the pump comes from our solar panels.

Hope that is some help.

Edwink

Rainwater Harvester

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