To grey water or not to grey water.

[MikeSharp01]

The very final decision we need to make before we pour the slab, and so fix the rainwater water drainage,  is whether to go for a grey water installation or not.

 

Experts of our acquaintance have said don't bother as they are more trouble than they are worth. However I noticed something on our water bill for the build this week, I don't usually look at it cos it's my other half's role and we don't have a water meter here at millstone manor. She showed me the bill and blew her top at the cost, it appeared to show that we had used 100m³ of water in the last 6 months! Anyway a quick look showed that it was an estimated reading, perhaps as they had shown up when the site was closed so could not access the meter, and in fact when I read the meter we had used 7m³ in the last 6 months. (Gives you an impression of how much coffee I drink) Anyway long story short I noticed that we pay sewage costs on 92.6% of the water through the meter and it struck me that we could reduce costs dramatically if we used grey water in the toilets etc. So what is the thinking out there, do I did a big hole and direct the rainwater to it or carry on and send it all to waste, anyone done the economics?

[PeterW]

Greywater and rainwater are two different things. Mixing them is not a good idea but essentially you need to decide if you go the rainwater route, what do you want to use it for and how much filtration etc you want to do. Also need to decide on a gravity vs pumped system and if it’s for eco reasons or financial ones ... 

[Russell griffiths]

The cost of installing it far out ways any saving on your water bill

it certainly did when I looked into it. 

[Onoff]

If you're going to dig a big hole what with the mess and spoil of it later now's the time to do it!

 

Just Google "uk future water shortage".

 

[Jeremy Harris]

I looked at whether filtering and re-using grey water was feasible, but read so many horror stories about problems with grey water storage, filtration and treatment that I decided against it.  If we had not had a borehole, I'd have fitted an underground rainwater storage tank, and used that for watering the garden and probably toilet flushing.  Rainwater is a LOT easier to use than grey water, from all I've read.  Bear in mind that grey water will always contain faecal coliforms, as well as other potential pathogens, in addition to a high phosphate concentration, from the surfactants used in body, clothes and dish washing products.

[MikeSharp01]

Sorry, its rainwater I want to harvest isn't it not the grey water as I have already paid for that on the input side and will get charged for it on the output side anyway so only advantage is the re-use bit and you only get one shot.

 

I need to reduce input side so rain water sounds like a good idea.

 

Anyway a tank will cost around £1500 and assuming install costs another £500, pipework, muckaway etc we into the game for around £2000 (plus labour). Looking at our diversity, toilet flushing / showing / washing / Washing up / Dishwasher / Baths only the toilet flushing bit is recoverable from the input side through straight rainwater harvesting. Our overall demand is a 60000l/pa of which toilet flushing will be 32000l/pa (32m³) we pay £1.7166 m³ for water and £2.39m³ for sewerage at the rate of 92.5% of delivered water. So toilets cost us £(32x1.7166)+((.925x32)x2.39) = £125.6752. Given this the simple, no allowance for NPV or such, payback time will be, wait for it £2000/£125.6752 = 15.9 years (or there abouts). So I think I can forget it on those grounds at least and given your comments above I think I will.

 

Thanks all.

 

32 

[Jeremy Harris]

You can install a rainwater storage system reasonably cheaply if you shop around.  IBCs hold 1000 litres each and can be picked from places like Smiths (http://www.smithsofthedean.co.uk/ ) reasonably cheaply, together with all the fittings needed.  @Bitpipe has a storage system that uses IBCs:

 

[Ferdinand]

@MikeSharp01

 

Have you an idea how much you will use on the garden and car etc? Rainwater for that will reduce your input volume.

Edited June 10, 2018 by Ferdinand

[joe90]

Rainwater for car cleaning and gardening is far better, I plan to use a big tank that I have to collect rainwater from my garage for this.

[Nickfromwales]

Can't water the garden or wash the car without cringing if your on a meter . 

Storing a load of rain water seems a no-brainer if you've got a digger there lying around. 

[Moira Niedzwiecka]

I will have a couple of water butts off the garage for the garden.

I have my car washed every 2 weeks for £5.

It means I can leave the car with the Albanian lads while I do my shopping & don't have to pay to park.

No brainer for me.

[PeterW]

3 hours ago, MikeSharp01 said:

Sorry, its rainwater I want to harvest isn't it not the grey water as I have already paid for that on the input side and will get charged for it on the output side anyway so only advantage is the re-use bit and you only get one shot.

 

I need to reduce input side so rain water sounds like a good idea.

 

Anyway a tank will cost around £1500 and assuming install costs another £500, pipework, muckaway etc we into the game for around £2000 (plus labour). Looking at our diversity, toilet flushing / showing / washing / Washing up / Dishwasher / Baths only the toilet flushing bit is recoverable from the input side through straight rainwater harvesting. Our overall demand is a 60000l/pa of which toilet flushing will be 32000l/pa (32m³) we pay £1.7166 m³ for water and £2.39m³ for sewerage at the rate of 92.5% of delivered water. So toilets cost us £(32x1.7166)+((.925x32)x2.39) = £125.6752. Given this the simple, no allowance for NPV or such, payback time will be, wait for it £2000/£125.6752 = 15.9 years (or there abouts). So I think I can forget it on those grounds at least and given your comments above I think I will.

 

Thanks all.

 

32 

 

Three IBCs is change of £120, pipes and pumps are £250, all told you should see change from £500...

 

Payback is now less than 5 years ...

[vivienz]

The price for rainwater storage varies according to whether you want a potable or non-potable supply. We plan to have a 10k litre underground tank with an extraction pump. It will only be used outside for the sake of simplicity but as I plan a kitchen garden and There will be loads of other gardening stuff going on, I figure it's well worth having.

I haven't got my figures with me right now but will post them tomorrow.

[vivienz]

Okay, the supplier I looked at is Tanks Direct Ltd.  For a 10,000l non potable underground water tank, delivered cost is £1,700 + VAT.  The estimated delivery time is 4 weeks.  It needs to be sunk to 2.635m and set in concrete.

[Bitpipe]

On 10/06/2018 at 22:41, PeterW said:

 

Three IBCs is change of £120, pipes and pumps are £250, all told you should see change from £500...

 

Payback is now less than 5 years ...

 

Yup - and you have the satisfaction of a jumbo up-cycling project.

[Dudda]

I'm using Hep2O manifolds in my plant room as done by other here. I put in three manifolds, cold water, hot water and rain water. The rain water manifold is fed by a small gravity header tank in the attic and the manifold feeds the WC's and outside taps. Now the header tank has two ball cocks. One for a rainwater tank in the garden and the other, a mains for when the outside rain tank is empty. The tank you put in the garden as you said is about 1,5000 to purchase. A big expense. I don't have the money currently for this so my rainwater header tank is currently fed from mains water as if the outside rainwater tank (which I don't have) is empty. The whole thing is working great and all I spent was €60 on a small header tank and two additional runs of Hep2O from the manifolds in the utility to the attic. If I ever decide to put the big expensive tank in the garden I can and the whole house is currently plumbed for it.

[Onoff]

1 hour ago, Dudda said:

I'm using Hep2O manifolds in my plant room as done by other here. I put in three manifolds, cold water, hot water and rain water. The rain water manifold is fed by a small gravity header tank in the attic and the manifold feeds the WC's and outside taps. Now the header tank has two ball cocks. One for a rainwater tank in the garden and the other, a mains for when the outside rain tank is empty. The tank you put in the garden as you said is about 1,5000 to purchase. A big expense. I don't have the money currently for this so my rainwater header tank is currently fed from mains water as if the outside rainwater tank (which I don't have) is empty. The whole thing is working great and all I spent was €60 on a small header tank and two additional runs of Hep2O from the manifolds in the utility to the attic. If I ever decide to put the big expensive tank in the garden I can and the whole house is currently plumbed for it.

 

So do you need non return valves on the mains in to the header to stop the rainwater back feeding into the mains?

[PeterW]

35 minutes ago, Onoff said:

 

So do you need non return valves on the mains in to the header to stop the rainwater back feeding into the mains?

 

No as a header tank with a ball valve is classed as an air gap however when they have the potential to be submerged then it’s recommended you use the Torbeck ones and adjust the floats accordingly. 

[Onoff]

31 minutes ago, PeterW said:

 

No as a header tank with a ball valve is classed as an air gap however when they have the potential to be submerged then it’s recommended you use the Torbeck ones and adjust the floats accordingly. 

 

I'll remember that. My one often cruds up with limescale and overflows. 

[Dudda]

The header tank came with the Torbeck float valve as its a rainwater header tank. It only has the Torbeck value on the rainwater income and a regular ball valve on the mains backup.

 

I actually do have a none return valve as an additional just in case. Its a Hep2O one so fits easily into the pipework. 

 

Having said that no water has or can come in that way yet as I don't have a source of rainwater.