rainwater harvesting and pumping

Hello,

I have installed a water butt and after a night of rain, it is now full to the brim but what to do with the water I have collected? I have read some of the old posts here and I see some of you use it for flushing toilets and supplying washing machines. It seems you pump the water into a header tank in the loft. How big a tank do you use: I'm thinking for a few toilet flushes and a run of the washing machine each day it must be a decent size?

How do you get the water into the loft? Do I have to have an ugly piece of MDPE on the side of my house? I read that MDPE is preferred because it will not burst when it freezes; why is that? Is it because the walls are thick?

It seems to me that you have to pump the water up to the header tank; couldn't you just miss out the header tank all together and pump the water to the toilets and washing machine? Would this be preferable? Would you get a better flow this way; what head do you get from the tank? Does it take forever for the toilets to fill by gravity?

It seems that either pumping to a tank or pumping to the "appliance" I will need a pump, but which sort: there are so many to choose from? I see that Tool station sell a bronze equivalent of a central heating pump, would this work for either application? It says it has a 5.5m head:

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also see that Machine mart sell submersible pumps:
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most expensive has a head of 35 metres so there should be no trouble pumping to the loft! I presume these would be what is required for pumping to the header tank? Would they also work for direct pumping...

Or would their range of centrifugal pumps be better for direct pumping:

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is even a bronze one and there is a controller to switch the pump on as required:
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these controllers reliable? has anyone seen them anywhere else (more cheaply?).

What about the pumps: are they noisy? I don't want to upset the neighbours with their noise.

Thanks, Stephen.

Reply to
Stephen
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Questions of my own:

1) What happens when the supply of rainwater runs out - i.e. how is the system arranged so that preference is given to supply from the rainwater, but normal mains water will take over if this is not available?

2) What happens during the colder (freezing) months - do people fit a manual shutdown, or some kind of automatic one, or just not bother and hope for the best?

3) How do the costs of running the pump compare to the savings in mains water costs (assuming somewhere with metered water)?

cheers

Jules

Reply to
Jules

The commercial systems have a mains water supply which is automatically switched over to if the rainwater runs out. I suppose a simple way of accomplishing the same thing in a DIY fashion would be to have a header tank with two ballcock valves, arranging things so the mains one kicked in at a lower level. You have to be careful not to contaminate the drinking water supply - mark pipes clearly as rainwater.

Another problem to solve is stagnant water in the header tank/toilets when you go on holiday (the water isn't treated you see). The commercial systems either do away with the header tank and have a pump with a flow switch feeding directly to the toilets/washing machine or else they dump the header tank water occasionally if it isn't used.

There's an argument between submersible pumps (cheaper, less noisy, likely to go wrong quicker) and having a wall mounted pump somewhere (need to find space, noisier, easier to service, but needs to be higher spec to raise the water out of an underground tank).

Also: what happens in the event of a power cut?

The fancier systems run everything inside or below the frost level underground.

The other advantage of having an underground tank is lack of algae growth due to the water being kept cool and out of sunlight. It's also easier to capture the entire water from the roof this way. Holes are expensive, though.

The figures I've seen show the electricity cost to be trivial (pence per month). The saving could easily be pounds per month - toilet and washing machine accounts for about half the average home's water usage.

The commercial systems are expensive, though: tanks start at about

700-800 quid (plus digging a hole to put it in and possibly concrete to hold it down in ground water, another 500-1000 quid), control systems and filters could easily set you back the same again. So payback is slow.
Reply to
Jim

two ballcocks in header tank? mains one set a lot lower than rainwater one? so header will never be"empty"....

to shut what down?

now you're getting it :>) plus costs of installing it and inevitable reairs/replacements/ "accidents"

I don't know abt 3 but I'm looking forward to see some more replies.......

cheers JimK

Reply to
JimK

^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Round here I seem to geta significant amount of dust / mud in the rainwater. Because my downpipe seems to be partially clogged (and therefore drains slowly) there's a lot of "earth" that precipitates out and fillts the gutter - to the point where things start growing up there. Is it a good idea to use rainwater for washing clothes? Maybe if you're careful not to stir up the sediment with your pump you might be OK. However, wouldn't it be better to have the water butt at roof height, rather than ground level so you you didn't have to pump the water back up? f

Reply to
pete

You need a decent filtration system if you're going to feed the washing machine - ie a silt trap, a leaf filter, a tank which overflows from the top to dispose of any scum, a filter on the input to the pump and then make sure that the water doesn't get too much sunlight or heat.

For a typical 2-3 bedroom house you're looking at storing 2-3 thousand litres to get through a couple of months of dry summer. I'm not sure how you suspend a tank that big (or even a quarter of the size) at roof height!

Reply to
Jim

True. (I'd originally thought two feeds, but my brain was thinking of them being set to activate at the same level - meaning you'd always get a mixture of both rainwater and mains; although perhaps that's no bad thing)

The rainwater feed. It might be best to drain the system to prevent freezing - not to mention that the extra cold water during certain months

*might* cause cistern condensation issues (if not on a modern insulated / lined cistern, anyway).

:-)

We're on a private well here anyway, so no water bills - but the well pump's quite large/noisy, and so something which results in that running less does have some potential I suppose.

The original post caught my eye as I do have a rain barrel on the back of the house doing nothing right now (it's too far from the veggie patch to be useful) so there's some scope for using rainwater for the toilets. I'll have about 50' of 3/4" pipe surplus when I re-jig the plumbing next year, so if a suitable pump and header tank happened to fall into my lap...

OTOH it freezes for 5 months here, so it's a lot of hassle for only 7 months of use out of the year :-)

cheers

Jules

Reply to
Jules

Makes sense - I just saw that in other Jim's reply.

Yeah, good idea. Although as mentioned in other reply we're on a private well here and haven't had issues with water sitting in cisterns when away

- but then I suppose the stuff in the ground, although untreated, has been filtered through the rock, unlike rainwater.

Hmm. I think our well pressure tank can cough out about a cistern-full of water without the pump running, so maybe something similar would work for the rainwater supply. That or just have a big enough header tank to do something useful via gravity-feed even if the power's out for a bit.

Annoyingly there was a old septic tank pulled out at our place right in the area where the guttering terminates - could have got 'em to pull the tank but not fill the hole in :-) All happened before we moved in, though...

We do have a basement here though, so I could quite easily put the tank in the basement and have it gravity-fed, with the pump to raise it up to the level of the house plumbing above - the only downside to that is the issues around power cuts that you mentioned, as then nothing would work without power.

Interesting. We wouldn't save anything there due to being on a well anyway, but I was still curious.

I'm not sure about running the washing machine on a system here (US) as washes are typically done in unheated water unlike the UK - and maybe the lack of heating will introduce nasties into the clothes that heated water wouldn't...

Yeah, screw that ;-) I expect a DIY could be done in a *lot* less though, but it assumes that the knowledge is out there in the public domain (like so many of these green schemes)

cheers

Jules

Reply to
Jules

If you have a header tank, you can then install two ball valves in it, one up high supplied by the raineater pump, and one of the floats set much lower, supplied fro mthe mains water. Then when you rainwater runs out or breaks down, the tank will just end up half full, and then get topped up with mains water. Make sure both of the valve parts are installed above the water line. Having a header tank will ensure your pump cant back-feed the mains water system with your rainwater.

You get two types of valves for your toilets, one for high pressure and one for low pressure (there is usually a small part you change in the unit to change between the two) so filling shouldn't take that long with the correct valve in the cistern.

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> I also see that Machine mart sell submersible pumps:

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> The most expensive has a head of 35 metres so there should be no

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> Are these controllers reliable? has anyone seen them anywhere else > (more cheaply?).

I have a submersible pump that is pretty quiet, can barely hear it from about 5m away - bought it form eBay several years ago...

As I have various taps around the garden, I needed a system that would pressurize the pipes, then cut the pump off, so I added a pressure vessel, a flow switch and a pressure switch and wired it so the pump is on when the pressure switch or the flow switch is not satisfied (So the two switches are just in parallel, and control a relay that turns the pump on) - once the pipes are fully pressurized, the flow will stop, and the pump then cuts off - drawing water will then (after about 5 liters) trigger the pressure switch, and then the flow switch then keeps the pump on until it is satisfied. I found i needed the flow switch, as the pressure switch was causing the pump to turn on and off rapidly, as the shock of the pump turning on was activating it.

I have since seen these on eBay which look like an all in one unit that is external, and therefore easier to maintain, and can be put inside a garage, or wherever.

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think you would still need a level sensor in the water tank it is pumping from, so it does not run dry.

Toby...

Reply to
Toby

fwiw

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Reply to
NT

Wait until the rain stops & use it to water the garden. Forget about the hare brained schemes to save the planet.

Reply to
The Medway Handyman

I would put the water butt on a hill or on a timber stand. When it's empty I would manually turn the mains tap on. However, my neighbour's water meter has not worked for a year or two. Is it wrong of me to connect up to his waterpipe?

Reply to
Matty F

Why do you need the pressure vessel, isn't the flow from the pump sufficient?

Reply to
Stephen

I agree that it would make sense if you could collect it at gutter height rather than letting it fall down the drain pipe and have to pump it back up, however one problem is that the gutter is slightly below the height of the eaves (or is it at eaves' height?), so even if you somehow took the drainpipe into the loft you would still need to pump it up and into the loft tank, albeit that you would only have to pump it a foot rather than thirty foot.

We all get dirt in our gutters and you would have to deal with this whatever height you collect the water at. I'm sure the majority of dirt comes from the gutter rather than the down pipe.

I suppose the best compromise would be to collect the rainwater just below the gutter and let it gravity fill a tank in the airing cupboard. This would let you gravity feed the downstairs toilet and washing machine and it might let you fill the upstairs toilet if the head was sufficient.

The weight of the water is a factor. The commercial tanks hold thousands of litres that, as other have said, you could not put in a loft but I was thinking more along the lines of a 25 gallon water tank, which would be supportable. You would need to supplement this with a larger tank on/in the ground if you wanted to run through long hot summers, if we ever get one!

Reply to
Stephen

I hadn't realised rainwater went so smelly so soon. Could you run the water through a pond UV filter, would that prevent it?

Reply to
Stephen

I think the cost of professional systems is the massive tank and the massive hole to put it in. A DIY system on a smaller scale might be very different. We have to pay an £80/year charge to the water company for them collecting our rainwater, so if all rainwater can be harvested we would save £80. Whatever electricity a pump would use will be less than £80, so after buying a couple of water butts, tanks, pumps, etc. it might pay back as quick as a couple of years and that's not considering any saving if you have metered water.

Reply to
Stephen

It doesn't, I store it.

Grey water is a different issue - you can't really store any quantity of that for any time, and you need to regularly flush tanks clean if that bothers you. In countries where its use is widespread, there are strict rules about how you use it, e.g. so you don't end up spraying the salmonela you washed off your hands all over your green salad plants.

Reply to
Andrew Gabriel

Or just make a soakaway.

MBQ

Reply to
Man at B&Q

I've been wondering about that. The lower ball will be completely submerged right? Doesn't that put a big load on the valve body, and hence the side of the tank? Or am I missing something?

R.

Reply to
TheOldFellow

That's true of an expansion tank too, when the system is in its expanded state. May not be completely submerged in all cases, but still forcibly held under water.

Reply to
Andrew Gabriel

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