Rainwater Harvesting...

[saveasteading]

6 hours ago, Gone West said:

a large underground brick and render tank

There is the answer.

Underground storage tanks without the rwh gubbins in them are not terribly expensive (I have found one we are obliged to install to store 10,000 litres for fire fighting.

About £1,000 for underground spec, plus the works.)

 

For garden use only, that or smaller, will collect all the water in a big storm and then a very simple pump can be used to water the garden/wash car. 

being underground it is much easier to collect all the water from all the rwp, albeit involving more drainage runs too.

[puntloos]

On 30/04/2022 at 14:50, saveasteading said:

There is the answer.

Underground storage tanks without the rwh gubbins in them are not terribly expensive (I have found one we are obliged to install to store 10,000 litres for fire fighting.

About £1,000 for underground spec, plus the works.)

 

For garden use only, that or smaller, will collect all the water in a big storm and then a very simple pump can be used to water the garden/wash car. 

being underground it is much easier to collect all the water from all the rwp, albeit involving more drainage runs too.

 

Reviving this discussion for.. obvious reasons. (hi, 40C!) 

 

My thoughts (given I'm doing a fully new build)

 

- Getting the digger to build me a major hole (next to? under?) my new foundations to fit some large plastic tank in seems pretty cheap.

- Trying to flush toilets etc with this seems very risky (mould, maintenance, complicated plumbing)

 

Id only collect rainwater for the garden, and in case of emergency, I would treat the water in my tank as "dangerous, be sure to use heavy duty 'tropical camping trip' style filters" if I ever resorted to use it for household purposes.

 

My questions:
- How much would it cost to dig a sizeable hole, rainwater tank, a little pump to send it round the garden, few surface pipes for said garden-spreading?

- How deep does such a tank usually sit? 1m of dirt on top of it? 1.5? Can my kid dig down to it when he's bored?

- How safe is this tank - can it collapse if we get fat aunt bertie running around with the kids or what if some future me forgets to tell the driver of a 1.5T digger to not drive on top? Trees poking their roots in? Is this a reason to put the tank below the house rather than below the garden/grass?

 

Edited July 17, 2022 by puntloos

[mike2016]

I'd be careful about digging next to your foundations, depending on the soil/type of foundations you may end up creating a fault/subsidence? 

Rainwater is fine for loo flushing if you want to take it into your house but needs double check valves and the rainwater tank in the attic has two balls, the second kicks in when you run out and fills up with mains water. This is handy also to flush the system with Chlorine from the mains before you go on holidays. But yep, retrofitting would be a pain. It can smell if left unattended for a long time. 

Simplest might be a pair of water butts to start with - overground so does take up space but gives you 400Litres to play with. Next is a plastic tank, long but not deep, can be buried just under the surface as long as it doesn't flood and you don't drive on it!! Third is the 3500L+concrete tank. Big Hole, can be just below the surface, that's a lot of mucking out though. You should look into a padlock / securing system if kids are around. They contain all the filters/pumps but do cost a lot. A DIY system and doing tanking yourself is a lot cheaper if you can crane this into position (over the house?!). 

The plastic tank would be the easiest after water butts I think. Shallow hole, can carry the butt through the side passage with two people and mini digger also. Connect it to a pump that has power with a garden hose outlet and should be under a grand I would have thought? No JCBs above it so plan location carefully and see what the suppliers say vs traffic over it and how to backfill. 

I've 2 x 200L water butts for years working great, gravity tap out of each with watering cans. Hope to do concrete 3500L tank with pump and greywater plumbing into house on my new build if I can afford it. 

[saveasteading]

The bargain design is this.

Second hand IBC, 1000 litres. , filled from a RWP.  Free to £50 depending on quality/ luck.

Join another any time using tank connectors, (or separately to another rwp.)

 

Cheap submersible pump for when you want to water the garden (£50 might be too powerful)

 

And apart from disguising the ugly tank there are no other costs.

 

You will get several fills per annum out of the tank, saving £3/m3...so about £20 per annum.

Capital repaid in 2 or 3 years plus you have done a good thing for the environment.

 

Plus, if you can avoid any rainwater going to the sewer you can get the sewage rate reduced.

[puntloos]

4 minutes ago, saveasteading said:

The bargain design is this.

Second hand IBC, 1000 litres. , filled from a RWP.  Free to £50 depending on quality/ luck.

Join another any time using tank connectors, (or separately to another rwp.)

 

Cheap submersible pump for when you want to water the garden (£50 might be too powerful)

 

And apart from disguising the ugly tank there are no other costs.

 

You will get several fills per annum out of the tank, saving £3/m3...so about £20 per annum.

Capital repaid in 2 or 3 years plus you have done a good thing for the environment.

 

Plus, if you can avoid any rainwater going to the sewer you can get the sewage rate reduced.

 

Not a bad idea but I really don't have space for anything in my back yard. I'm looking for under the house, or under my back yard. 

Or is that a hugely different proposition? 

 

I'm somewhat considering using the space below my ASHP (in the garden) since that will already have a concrete foundation?

 

[saveasteading]

7 minutes ago, puntloos said:

is that a hugely different proposition? 

Yes. Under the house is complex and expensive.

Under the back yard is ok unless close to the house or if there will be vehicle loads.  But the tank will cost £1,000 to buy and install, not £50.

[puntloos]

5 minutes ago, saveasteading said:

Yes. Under the house is complex and expensive.

Under the back yard is ok unless close to the house or if there will be vehicle loads.  But the tank will cost £1,000 to buy and install, not £50.

 

1000 is fine given the full cost of my build (ouch). My only concern like you said is if the tank somehow collapses under loads. Not planning to drive anything significant across it but I would prefer to have it seated deep - 1m of soil above it? - and safe (reinforced somehow?) rather than shallow and have my kid puncture it when he plays with his tonka truck.

 

One important question for me is that it 'feels' like having a big tank under the ground might impede the growth and flourishing of things like my lawn etc. Is that an issue at all?

 

I might give rainwaterharvesting.co.uk a call.

Edited July 17, 2022 by puntloos

[Ferdinand]

One of things to be said for above ground is that you can get a gravity feed.

 

I have 3 linked Wickes water butts for 600l of stored water, one of which is plumbed in (with a piece of hose pipe) to an automatic watering network for my container plants and newly planted bushes, The advantage of that is that rather than turning it on from a tap (which would need a double tap) or a pump I just leave it to drip out with the 0.5m of head for half a day.

 

If butt 1 runs dry I just move the hose to butt 2. Butt 3 is for the watering can.

 

This year it is noticeable how much intermittent rain we have continued to have.

 

If I go on hols it is slow enough that it lasts nearly a week until it has emptied one butt.

 

But - horses for courses.

[puntloos]

3 minutes ago, Ferdinand said:

One of things to be said for above ground is that you can get a gravity feed.

 

I have 3 linked Wickes water butts for 600l of stored water, one of which is plumbed in (with a piece of hose pipe) to automatic an watering network for my container plants and newly planted bushes, The advantage of that is that rather than turning it on from a tap (which would need a double tap) or a pump I just leave it to drip out with the 0.5m of head for half a day.

 

If butt 1 runs dry I just move the hose to butt 2. Butt 3 is for the watering can.

 

This year it is noticeable how much intermittent rain we have continued to have.

 

If I go on hols it is slow enough that it lasts nearly a week until it has emptied one butt.

 

But - horses for courses.

Yeah, but with a teensy garden I have very little option but go down. Like the idea of gravity etc but eh, not a dealbreaker to pump, I imagine? One of my worries is indeed "crap" (literally bird..) accumulating at the bottom of such a tank, especially if it's deep underground and hard to get to..

 

 

 

 

[saveasteading]

12 minutes ago, puntloos said:

One of my worries is indeed "crap" (literally bird..) accumulating at the bottom

Don't worry. It is good for the garden and dissolves. Just keep solids out with some mesh. 

[Kelvin]

We looked into this too for our new build. We have a borehole so the thought was to reduce the water abstraction from the borehole  rather than flashing it down the loo. Setting aside the ROI as that wasn’t a significant consideration, what point me off was:

 

1. over complicated plumbing for the house

2. failure of RWH pumping which seems to be a given 

3. the mess it can make of cisterns etc. I went to see a few installed systems and had a sneaky peak in their cisterns and all were fully of black mould. My assumption was this was just bad design and poor ongoing maintenance 

4. The size of the tank for it to make sense 

 

In the end we diverted the cash to PV/batteries. 
 

If you want to remove your lawn watering guilt completely then don’t water it at all. The lawn doesn’t really need watering and if you do water it, it needs a huge amount of water as too little water can encourage poor root growth. 
 

 

[SteamyTea]

34 minutes ago, Kelvin said:

In the end we diverted the cash to PV/batteries. 
 

If you want to remove your lawn watering guilt completely then don’t water it at all.

Very good point.  I don't have a lawn, and would never water one if I did.

I have the most expensive tap water in the country, so don't wash my car either.

[saveasteading]

2 hours ago, Kelvin said:

failure of RWH pumping which seems to be a given 

Yes, pumps fail and service can be slow. We foresaw that for our own office construction, and installed a shortcut from mains to the internal system, so turning one valve off and another on was all that was required.

As you say, it can be complex.

[SteamyTea]

5 minutes ago, saveasteading said:

can be complex

Larger pump and an accumulator.

2 parts that way.

[puntloos]

Thanks for the insightful stuff. 

3 hours ago, Kelvin said:

We looked into this too for our new build. We have a borehole so the thought was to reduce the water abstraction from the borehole  rather than flashing it down the loo. Setting aside the ROI as that wasn’t a significant consideration, what point me off was:

 

1. over complicated plumbing for the house

2. failure of RWH pumping which seems to be a given 

3. the mess it can make of cisterns etc. I went to see a few installed systems and had a sneaky peak in their cisterns and all were fully of black mould. My assumption was this was just bad design and poor ongoing maintenance 

4. The size of the tank for it to make sense 

 

In the end we diverted the cash to PV/batteries. 
 

If you want to remove your lawn watering guilt completely then don’t water it at all. The lawn doesn’t really need watering and if you do water it, it needs a huge amount of water as too little water can encourage poor root growth. 

 

Hm. Perhaps I should stick with this approach. I guess I was thinking a little bit about droughts as well. Perhaps one approach I could consider is just sinking that tank into my garden and only connecting it if and when it starts to make sense...

[joth]

17 hours ago, saveasteading said:

Yes. Under the house is complex and expensive.

Under the back yard is ok unless close to the house or if there will be vehicle loads.  But the tank will cost £1,000 to buy and install, not £50.

 

FWIW - going the main contractor route and paying the home counties tax (both of which will apply to @puntloos too I believe) the cost increase for submerged RWH tank (vs a standard soak away) was +5000 gbp on the quote, not 1000. That includes the additional much cart away, supply+install of tank, and the additional plumbing & electrics.

 

Needless to say, we ditched the idea and got a couple water butts instead. 

 

(Our price was quoted 2019 so who knows where it stands today.)

 

 

[puntloos]

6 minutes ago, joth said:

 

FWIW - going the main contractor route and paying the home counties tax (both of which will apply to @puntloos too I believe)

What is this tax you speak of?

6 minutes ago, joth said:

the cost increase for submerged RWH tank (vs a standard soak away) was +5000 gbp on the quote, not 1000. That includes the additional much cart away, supply+install of tank, and the additional plumbing & electrics.

Critically though, you are talking about plumbing the house to make use of the water? 

That part I wouldn't do anyway...

 

6 minutes ago, joth said:

 

Needless to say, we ditched the idea and got a couple water butts instead. 

 

(Our price was quoted 2019 so who knows where it stands today.)

 

 

But but but Zombie attack. Mad Max preparedness. 

 

OK. I guess I'll invest in more solar, but just mention it as an aside.

 

[saveasteading]

2 hours ago, joth said:

the tank will cost £1,000 to buy and install, not £50.

That is a 2m3 plastic tank, not a 5m3 harvester system.

 

Water butts are good. If you watch the market they vary from £25 to £50 for the same model.

[joth]

12 hours ago, puntloos said:

Critically though, you are talking about plumbing the house to make use of the water? 

That part I wouldn't do anyway...

Yes but all the plumbing was only£800 of the 5k, and some amount of that would have been charged anyway just to plumb it to an outdoor tap...