Rainwater harvesting

[Pocster]

Whilst I did plan to have this with one of those nice fancy tanks and automated controller - I’m starting to wonder ....

Its uses are toilets , washing machine and garden .

Ignoring garden water - there isn’t really a massive saving . Also I’m less keen to have ‘roof’ water staining my nice toilet !

Tempted to drop it ( and save cash )

Garden though still worth it . So I can easily set a cheap tank underground but assume I’ll need to pump it out to get good hose pipe type pressure . So a simple tank with some kind of pump ???

 

I have a vague recollection this may have been discussed before .... ?

Edited September 26, 2019 by pocster

[Jeremy Harris]

I'm not sure I'd use rainwater with a washing machine, TBH, given that they tend to run pretty cool nowadays.

 

The cheapest option is to use IBCs, they normally hold 1000 litres each and can be obtained fairly cheaply as surplus.  They need care if being buried, though, as they may not tolerate soil pressure that well without some reinforcement.  Easy enough to just drop a submersible pump in a tank and connect it up to a pressure vessel and pressure switch so that the pump runs when the pressure drops.  This is essentially how our borehole supply works.

[Pocster]

6 minutes ago, JSHarris said:

I'm not sure I'd use rainwater with a washing machine, TBH, given that they tend to run pretty cool nowadays.

 

The cheapest option is to use IBCs, they normally hold 1000 litres each and can be obtained fairly cheaply as surplus.  They need care if being buried, though, as they may not tolerate soil pressure that well without some reinforcement.  Easy enough to just drop a submersible pump in a tank and connect it up to a pressure vessel and pressure switch so that the pump runs when the pressure drops.  This is essentially how our borehole supply works.

Yeah ; I’ve pretty much convinced myself this is the way to go . But it’s nice to get it approved by you @JSHarris

[joe90]

I looked into rainwater harvesting for our toilets etc but apart from collecting rain on the workshop for the garden and car washing I decided to forget it.

[Pocster]

So what’s the best way to deal with potentially the tank empty ? I.e I really don’t want mains water ( meter ! ) filling it up !!! .

So i’m Guessing if tank empty you automatically ‘swap’ to mains . Best way to achieve that ??

Edited September 26, 2019 by pocster

[Jeremy Harris]

16 minutes ago, pocster said:

So what’s the best way to deal with potentially the tank empty ? I.e I really don’t want mains water ( meter ! ) filling it up !!! .

So i’m Guessing if tank empty you automatically ‘swap’ to mains . Best way to achieve that ??

 

 

You'll need some form of level sensor in the tank to signal that it's empty, plus a change over valve system to switch to mains.  This will need some thought, as the regs require that the mains water side be kept isolated at all times from the rainwater side.  Might need an additional buffer tank and pump, so that an air gap can be maintained for separation.

[Pocster]

5 minutes ago, JSHarris said:

 

 

You'll need some form of level sensor in the tank to signal that it's empty, plus a change over valve system to switch to mains.  This will need some thought, as the regs require that the mains water side be kept isolated at all times from the rainwater side.  Might need an additional buffer tank and pump, so that an air gap can be maintained for separation.

Erm ! Might it just be easier ( say you are using the hose and tank runs dry ) that you manually turn a tap to start filling the tank from the mains ..... ????

Edited September 26, 2019 by pocster

[Pocster]

I mean maybe a mains tap simply above the tank - so no physical connection.....

[Jeremy Harris]

If you pump from the rainwater tank to a small open header tank, and use a float switch in the header tank to control the rainwater tank pump, you can then either use gravity to supply water from the header to the toilets etc, or another small pump.  You'll need something to stop the rainwater tank pump from dry running and killing itself, so that means some sort of float switch in the main tank to detect when it's empty and turn the pump off.  You can then arrange a float valve in the header tank to fill that with mains water when the level drops, as the level should only drop a lot in that tank when the rainwater tank is empty.

 

All told it's a bit of a faff, IMHO, for the modest mains water savings that might be achieved.  @Bitpipe probably has the simplest system, just a collection of IBCs piped together and gravity fed with rainwater.  There are some photos here somewhere showing his system, I think.

[MikeSharp01]

1 hour ago, JSHarris said:

This will need some thought, as the regs require that the mains water side be kept isolated at all times from the rainwater side.

Anything to stop you topping up the collecting tank from the main would cut out the dual pipework? You could break the direct connection by having a valve that dumps mains water into the gutter although that might fall foul, pardon the pun, of a hose pipe ban.  

[PeterW]

Top up systems come in many shapes and sizes but at £200 plus they aren’t cheap. Biggest issue is they all need a class 1 air gap between the mains and the rainwater supply. 

 

This is just one example. https://steelpumps.co.uk/product/electronic-mains-water-top-up-with-pump-isolation-and-alarm/

 

You could make one for about £20 based on that picture.  

[MikeSharp01]

1 hour ago, PeterW said:

This is just one example. https://steelpumps.co.uk/product/electronic-mains-water-top-up-with-pump-isolation-and-alarm/

Yep interesting link - as you imply money for old rope.

[Ferdinand]

18 hours ago, pocster said:

So what’s the best way to deal with potentially the tank empty ? I

 

Cacti or Manchester ?

Edited September 27, 2019 by Ferdinand

[ToughButterCup]

19 hours ago, JSHarris said:

[...] There are some photos here somewhere showing his system, I think.

 

Here they are.

Important lesson (for me anyway): cheap IBCs need an expensive boudoire in which to keep them. And  that's a shame. The idea of waterharvesting attracts.

Time to hunt for some cheap  (how to put this? ) surplus concrete: a bin end if you like.

[Vijay]

14 minutes ago, AnonymousBosch said:

 

Here they are.

Important lesson (for me anyway): cheap IBCs need an expensive boudoire in which to keep them. And  that's a shame. The idea of waterharvesting attracts.

Time to hunt for some cheap  (how to put this? ) surplus concrete: a bin end if you like.

 

What about an old concrete panel led shed/garage, that could be put back together in ground?

[Pocster]

6 minutes ago, Vijay said:

 

What about an old concrete panel led shed/garage, that could be put back together in ground?

Or just some simple shuttering and a few barrows of concrete ...

[Bitpipe]

11 minutes ago, AnonymousBosch said:

 

Here they are.

Important lesson (for me anyway): cheap IBCs need an expensive boudoire in which to keep them. And  that's a shame. The idea of waterharvesting attracts.

Time to hunt for some cheap  (how to put this? ) surplus concrete: a bin end if you like.

 

Correct, as I had the expensive boudoir a cheap solution made sense.

 

I also bought a cheap 1100W pump (£40 Amazon) to get the water to ground level - which is a 2.8m rise. The pump could only really generate about another metre of head so the sprinkler is decidedly underpowered, when attached to the mains it has a 3m head.

 

So an interesting experiment but I rarely use the stored water as in the summer, that tank will barely cover the lawn and in winter it's wet anyway. Maybe when we have a few more flowers etc I will get more use out of it.

[Pocster]

5 minutes ago, Bitpipe said:

 

Correct, as I had the expensive boudoir a cheap solution made sense.

 

I also bought a cheap 1100W pump (£40 Amazon) to get the water to ground level - which is a 2.8m rise. The pump could only really generate about another metre of head so the sprinkler is decidedly underpowered, when attached to the mains it has a 3m head.

 

So an interesting experiment but I rarely use the stored water as in the summer, that tank will barely cover the lawn and in winter it's wet anyway. Maybe when we have a few more flowers etc I will get more use out of it.

What kind of pump would be required to generate ‘hose pipe ‘ pressure ??

Misses never likes a dribble ... 

[ToughButterCup]

2 minutes ago, pocster said:

Or just some simple shuttering and a few barrows of concrete ...

 

I'm knackered enough to wince at the word barrow, & now the quack tells me I have an arthritic shoulder : but thanks for the thought.

A couple of years ago, I bumped into a local who makes concrete like this .... 

 

one of the most interesting guys I have ever talked to: cheerful as a Lottery Winner. Top bloke - for a self builder.

I can feel a little visit coming on.

If you've driven past Lancaster on the M6, you driven past his 'yard' 50 meters from it in fact.

[Pocster]

1 minute ago, AnonymousBosch said:

 

I'm knackered enough to wince at the word barrow, & now the quack tells me I have an arthritic shoulder : but thanks for the thought.

A couple of years ago, I bumped into a local who makes concrete like this .... 

 

one of the most interesting guys I have ever talked to: cheerful as a Lottery Winner. Top bloke - for a self builder.

I can feel a little visit coming on.

If you've driven past Lancaster on the M6, you driven past his 'yard' 50 meters from it in fact.

Coorrrrr ! Puts @Onoff inventions to shame ! 

[ToughButterCup]

1 minute ago, pocster said:

Coorrrrr ! Puts @Onoff inventions to shame ! 

 

Aaah tell thee lad, aahve sin sum stooof up at 'is place as 'd mek yer ears droop wi' jealousy.

Sum on it, well ..... it'd tek thee breath. (tr. kill you)

[Jeremy Harris]

15 minutes ago, pocster said:

What kind of pump would be required to generate ‘hose pipe ‘ pressure ??

Misses never likes a dribble ... 

 

 

Any borehole type submersible pump will do the job.  A cheap Polish one can be had for around £100, that will generate around 8 to 10 bar.  We run our house at a water pressure of between 2.5 bar and 3.5 bar, and that's plenty for a powerful hose or sprinkler.  I've used (in fact am still using at the moment, as I still haven't got around for swapping it for the new Grundfos that's sat here) one of these Polish pumps: https://www.ebay.co.uk/itm/IBO-3-SQIBO-0-75-Borehole-Deep-Well-Submersible-Water-PUMP-House-Garden-cable14m/172266241359?hash=item281bde3d4f%3Ag%3AVDIAAOSwm3ldZ89L&LH_BIN=1

[Bitpipe]

39 minutes ago, JSHarris said:

 

 

Any borehole type submersible pump will do the job.  A cheap Polish one can be had for around £100, that will generate around 8 to 10 bar.  We run our house at a water pressure of between 2.5 bar and 3.5 bar, and that's plenty for a powerful hose or sprinkler.  I've used (in fact am still using at the moment, as I still haven't got around for swapping it for the new Grundfos that's sat here) one of these Polish pumps: https://www.ebay.co.uk/itm/IBO-3-SQIBO-0-75-Borehole-Deep-Well-Submersible-Water-PUMP-House-Garden-cable14m/172266241359?hash=item281bde3d4f%3Ag%3AVDIAAOSwm3ldZ89L&LH_BIN=1

 

May look into that - the cheap pump died and I got a refund from Amazon so was planning to get a new one next summer.

 

Does it need to be upright or would it work on its side?

[Jeremy Harris]

15 minutes ago, Bitpipe said:

 

May look into that - the cheap pump died and I got a refund from Amazon so was planning to get a new one next summer.

 

Does it need to be upright or would it work on its side?

 

 

They work fine on their side.  The only thing to watch is that they are a positive displacement pump, so they need to be turned off before a tap is fully closed, or have a pressure vessel and switch to turn the pump on and off.  Might be an idea to just fit a cheap pressure relief valve in the outlet as a safety device.  If the outlet is turned off or completely blocked the pressure rises to a very high level.  I've accidentally done this and had a 15 bar pressure gauge pegged at the end stop.  IIRC, 15 bar is way over the maximum pressure for normal MDPE pipe.

[Bitpipe]

5 minutes ago, JSHarris said:

 

 

They work fine on their side.  The only thing to watch is that they are a positive displacement pump, so they need to be turned off before a tap is fully closed, or have a pressure vessel and switch to turn the pump on and off.  Might be an idea to just fit a cheap pressure relief valve in the outlet as a safety device.  If the outlet is turned off or completely blocked the pressure rises to a very high level.  I've accidentally done this and had a 15 bar pressure gauge pegged at the end stop.  IIRC, 15 bar is way over the maximum pressure for normal MDPE pipe.

 

Ok, that's good to know - I just attached a garden hose to the end of the old pump with a 1" to hozelock fitting but this one will obviously need some better thought!