What rainwater harvester would you recommend, for flushing and perhaps washing machine?

[CalvinHobbes]

Been looking at the Graf rainwater system - maybe the 3000l platin? So 4 bedrooms, would like it for flushing and washing machine. Was wondering has anyone any advice? Obviously trying to keep the costs as low as poss. Also when do we put the tank in, is it when the digger is there doing the foundations?

Edited November 28, 2022 by CalvinHobbes

[Nickfromwales]

Will you be running outside taps off this also, for gardening / window cleaning / jet washing patios? If not, then I wouldn’t install one tbh, as the investment doesn’t ever look holistically kosher to me when I’m asked to include one for a new build client. Unless you’re maximising the savings by seriously offsetting your mains water dependable then I’d seriously spend this money on more PV which makes far more sense.
 

Cost of system plus cost of installation, maintenance / cleaning filters, inevitable pump replacement, additional segregated plumbing system in the house, electrical consumption during operation etc etc vs just buying water from the mains doesn’t make sense at all to me, unless you go for a huge tank say 10,000L which WOULD make sense, just about.

 

I’ve recommended to a recent few clients not to bother with RWH unless the size of the tank is a minimum of 7-8000L, as when you get a dry spell <2500L of a typical 3000L tank will be gone quite quickly and you’ll be back to running off mains supply anyways. When it’s raining there’s more water than you’ll need even for outside taps etc as the garden is already wet and you’re inside in the dry not using them / washing car / windows / patio etc.

 

Then add the inconvenience of typically having to have an indoors break tank for the pump to fill, which means you then have a gravity feed to WC’s and W/M, and then that’s me out completely. Most modern cisterns won’t be suitable for such low pressure supplies, and I had to swap out the fill valves on the 1st floor WCs for one client ( who had already self installed the tank ). You’ll need ‘attic’ space to install this coffin tank if you want any useful pressure ( head ), and access to it for maintenance, plus accept the noise of it filling and emptying. Or, depending on the size of system, you may need an accumulator for attenuation if the gravity break tank isn’t an option.

Another pita is, when you eventually need to run off potable mains water, that will be when you prob still have over 500L or more left in a 3000L tank, ( eg when the pump float drops down and mains feed system kicks in to top you up from metered, potable water ) and that 500L capacity is rendered unusable for the lifetime of the system. Not sure if some manufacturers state useful capacity vs capacity? Salespeople rarely dwell on negatives btw  This system is designed to not fully fill the tank when consuming potable mains water, so, for periods of little or no rainfall ( aka summer ) the frequency of the pump running will be far greater than in the rainy seasons, further labouring and fatiguing the expensive pump.

 

Then the mains filling ( run dry / failsafe ) system needs detailing;

This is normally achieved by installing a rainwater gulley trap in the floor under the stairs / utility / other inside the dwelling, and a cold mains water feed then gets poured into this via a solenoid and an open pipe feeding mains water into a tundish > gulley, eg to eventually get to the tank but purposefully indirectly . FYI, you are NOT allowed to install the cold water feed in the turret of the tank as RHW is classed as Cat5 water ( as bad as sewerage ) and an A/B ( iirc ) air break between potable mains supply and the RWH must exist for water bylaws compliance. For a previous client, we ended up putting this into the garden shed, as there was zero chance ever of me installing a rainwater gully inside a residential domestic dwelling!! Plus the noise of the water gushing into an open tundish would be less than ideal afaic. That could be timed but it’s not recommended, ergo this could go into ‘fill mode’ whilst you’re trying to shower, sapping valuable cold mains pressure for extended periods of time, and often…….

 

The pump failing once every 10 years will pretty much wipe out that decades savings for a small capacity system. Looks great on paper no doubt, but not in reality.  

 

So, no from me, unless the numbers make sense, which they don’t. Buy more PV instead.

[SteamyTea]

50 minutes ago, Nickfromwales said:

3000L tank will be gone quite quickly

Would save me 21 quid each time though.

[ProDave]

Oh the joys of not being metered for water.

[Nickfromwales]

32 minutes ago, SteamyTea said:

Would save me 21 quid each time though.

Nope. 

[Nickfromwales]

30 minutes ago, ProDave said:

Oh the joys of not being metered for water.

Likewise. 

[SteamyTea]

1 minute ago, Nickfromwales said:

33 minutes ago, SteamyTea said:

Would save me 21 quid each time though.

Nope. 

3 m³ of water costs me £21, so apart from some relatively small running costs, would soon add up if I did normal things like washing a car and watering a garden.

I have had about 900mm of rain this year (exceptionally low), if I used half of that, it would save me £100/year.

[Nickfromwales]

3 hours ago, SteamyTea said:

3 m³ of water costs me £21, so apart from some relatively small running costs, would soon add up if I did normal things like washing a car and watering a garden.

I have had about 900mm of rain this year (exceptionally low), if I used half of that, it would save me £100/year.

So with a conservative install cost of £5k start to finish you’d need to be able to completely fill and completely empty this ~240 times to cover purchase price, without ever using the mains.

 

[SteamyTea]

16 minutes ago, Nickfromwales said:

So with a conservative install cost of £5k start to finish you’d need to be able to completely fill and completely empty this ~240 times to cover purchase price, without ever using the mains.

 

Yes.

As I have been in this house for over 17 years that is 15 times a year, under 50 m³.

Now if I was in the very dry  Thames Water area, where water is a lot cheaper than in the very wet South West, it would take a lot longer to pay for itself.

It really comes down to how cheap your water and waste is.

I cannot see that the rain water harvesting cannot be run at the same time as mains water. What is to stop me filling the bog at the same time as watering the garden?

Like PV, systems can be designed to cope with both inputs easily.

 

Retrofitting could be expensive, but if designed in from the start for a new build, the costs should be pretty low. Also would not be hard, or expensive, to fit an ozone steriliser to a pumped system. 

Just takes a bit of design imagination. So best to not ask an architect to do it.

[Marvin]

13 hours ago, CalvinHobbes said:

Been looking at the Graf rainwater system - maybe the 3000l platin? So 4 bedrooms, would like it for flushing and washing machine. Was wondering has anyone any advice? Obviously trying to keep the costs as low as poss. Also when do we put the tank in, is it when the digger is there doing the foundations?

It's really sad, but rainwater harvesting is a real tricky thing to justify.

The time that you want to use it most, is the summer when it's dry, and the time you need it least, well er, now.

 

We have rainwater storage only which is used for watering plants and filling the loos. 4000ltr approx. Dries out in summer.  Full all winter. We have to have 2 seperate supplies for the loos.  1 mains back up one rainwater.

 

If I had any option again I would increase the tanks to 10000ltrs but still only supply plants and loos and spend any budget I was going to use on rainwater harvesting on additional insulation and  additional PV.

 

GOOD LUCK!

 

M

 

[saveasteading]

Agreed most or all of the above.

I put a 10m3 harvester in for our own office...no client wanted one but we would test it.

100% of roof water into tank. Double the suggested size.

It never ran out of water.

The big bonus was that sewage charge was based on water use, so also tiny. And small water pipe in reduced rates.

Saving apparently huge.

Environmental benefig big too...less water bought and disposed of.

But I have no idea the electric cost for the pump. The pump broke down and polypipe weren't interested.  Got a repair eventually. Pump broke down again. Leased the building and tenant not interested so harvester sits unused as an expensive manhole.

Moral....I might do one for myself, but wouldn't recommend it.

But rainwater butts are simple and good as are soakaways and ponds.

 

[SteamyTea]

3 minutes ago, saveasteading said:

The big bonus was that sewage charge was based on water use, so also tiny. And small water pipe in reduced rates.

Saving apparently huge.

I have a feeling that the water companies can still charge for waste, even if not metered.

It is the waste water down here that costs the most.  Can't have our beached covered in human waste, dogs will get upset, then slink off and dump in the street.

 

 

Still, the residence of S. Agnes like to think their organic, locally produced wholefood shit don't smell.

 

 

 

[Nickfromwales]

1 hour ago, SteamyTea said:

I cannot see that the rain water harvesting cannot be run at the same time as mains water. What is to stop me filling the bog at the same time as watering the garden?

Like PV, systems can be designed to cope with both inputs easily.

They can be run at the same time, but my point was during summer ( most of it ) where the RWH tank cold fill system would be filling off the mains at the same time you want max cold mains potential yourself for showers etc, even more of an annoyance if the supply is already meagre.

Filling the bog is not life or death, nor any appliances, they’ll just ‘eventually’ fill, but if you want a shower then it’s likely ( and no, not for you ) that the DHW device will be very much cold mains dependant. 👎. 
 

32 minutes ago, Marvin said:

We have to have 2 seperate supplies for the loos.  1 mains back up one rainwater.

How is this set up? When I checked the regs you could not create a physical link between RHW and the potable mains supply, so no 2 position valve etc ( or a setup like a softener bypass ) is permissible. 
The only thing I could see to do this with was a boiler filling loop, 2 lots of double check non returns, and a removable filling link which could only be connected to one or the other, and NEVER the two supplies together. 

[Marvin]

Hi @Nickfromwales

 

We have a small tank in the loft with a potable mains supply via a double check valve feeding ball valve 1, and a float switch operating a pump on the rainwater side feeding ball valve 2. The loos are then gravilty fed.

 

The ball valve on the rainwater side is an over filling precaution along with the overflow pipe.

 

M

Edited November 28, 2022 by Marvin
Spellingggg

[Blooda]

We have a 7500l system, with attenuation.  Supplying a tank in the loft and then to toilets.  The overriding factor in installing was the fact we had to attenuate flow to a combined sewer, a requirement for the water board.

 

During the design phase, we paid a SE to come up with an expensive system, that included attenuation crates, and a vortex valve, that really was overkill, and more suited for larger developments.  We went to Rainwaterharvesting.co.uk , who "designed" their system to meet our attenuation requirements.   

 

Having lived with it now, for a few months, I agree with most things said on here, but for our build, it was the least expensive of the systems.  And we had to get it in the back garden, before the foundations went in, During April / May 2020, whilst most of the country was sunning themselves in hot tubs on Furlough, and not speaking to customers.  

 

 

 

 

 

[saveasteading]

2 hours ago, SteamyTea said:

have a feeling that the water companies can still charge for waste, even if not metered.

I'm sure they can do whatever they like. Ours was very precisely linked to mains water used...and as it was an office there was mostly wc use, plus outside tap. Mains water to kitchens and to barely used shower.

Also, as no rainwater went to mains drains, (unless via wc) , there was another discount.

There was an attenuation requirement too, but we used all soakaway and lagoon, so no crates required.

[Jenki]

35 minutes ago, saveasteading said:

 

There was an attenuation requirement too, but we used all soakaway and lagoon, so no crates required.

Have you any details on the lagoon design? 

I've not researched this yet, but I'm finding that on out site It might be prudent for us to hold some water back. 

I was planning RWH for the house, and the latest rain has confirmed I need to do something, as the rubble drain for our treatment plant has backed up recently 🤔 I've got about 4 acres of field draining towards the coast past my treatment plant and not getting past my new track, so currently pumping this to help it on its way to the sea.

I've got some more stone on the way to bring the level of my track back to the original field level, so it doesn't pool.

[CalvinHobbes]

Oh that fair put me off.  Thanks for the reality check. So what if we put in a pipe through the blocks during the build (and suitably encase it with insulation so that in future years if the metering because too pricey, we could add it in without compromising the thermal envelope? TBH would prefer to put the money towards better windows and a better metal roof.

[Benpointer]

We put in a 3500l rainwater harvesting system when we did our house 12 years ago, for WC flushing, running the washing m/c and garden watering.  

 

I wouldn't do it again.  Issues include:

• The water is of course unchlorinated, so you get brown toilet u-bends after a while (and the insides of the cisterns go black with mould, not that you see those of course).
• The washing never felt entirely 'clean'.
• We switched the toilets and washing m/c to mains after a few years for the above reasons.
• The tank ran out regularly each summer and the automatic top-up seemed to waste quite a bit of water down the tank overflow as it was delivered to the tank via the  drainpipes and thus the leaf filter.
• The pump failed after 8 years and cost about £300 to repair (versus £700 to replace)
• The electric controller failed last year, so now we just switch the pump on manually when we want to water the garden.
• And it still runs out as soon as we have a dry period (ok we have a big garden and a lot of watering.

So in short: nice idea but really not worth it.  It's certainly never paid for itself.

 

Sorry to be negative.

[ToughButterCup]

Our rainwater is harvested by our pond,  water garden and water butts. All the water from the roof and road is ducted to a water garden, the overflow of that to a massive (5 tonne) underground sand filter. That overflow goes into the pond. If there's anything left over it goes into the water butts.

 

The pond overflowed twice this year.

It didn't make financial sense to use rainwater inside the house. The current arrangement saves a good deal of effort in the garden.

[saveasteading]

Stopping or slowing water going to runoff is a very good thing. 

Do it for the greater good.

 

Water butts, yes.

Ponds are good too.

Rainwater into the house is not usually justifiable in cost or on sustainability (carbon)  grounds.