Y-valve to select between rainwater and house water?

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Our garden taps run off a rainwater system, which also feeds the toilet cisterns. Separately, we have a pressurised cold water system in the house feeding showers, bathrooms, etc.

During dry periods, we often run out of rainwater leaving us with no garden taps -- kind of a pain since that's exactly the time you need water for gardening. The toilets come through a buffer tank in the attic that gets topped up from mains if the rainwater runs dry, so no issue there; however, the garden taps are fed directly from the underground tank.

Our three-year old likes to turn on the garden taps and then leave them on, which is a great way to drain the system entirely.

So, I'd like to add a valve of some kind that will allow manual switching of the garden taps between the pressurised water system and the rain water system, ideally with a third setting that turns off the supply to the taps completely.

Is such a valve a standard plumbing fitting? I'd have thought so, but can't seem to find it on any of the plumbing websites. Possibly I just don't know the correct terminology.

I'd be happy to splurge for a motorised valve if it meant I could move the control for it to another location; our plant room has a ton of valves in it already, so adding one more is not going to be very wife-friendly.

(In an ideal world, the system would automatically switch from rainwater to house supply when the rainwater runs out; however, any suggestions I've seen for setups to do this involve 1-way valves to stop backfeed of the grey rainwater into the main water system, and 1-way valves don't appear to be 100% reliable -- a failed valve in that scenario would be hard to detect, with possible health implications. So, a manually switched system seems safer.)

Anyway, I'm sure this is all bread & butter stuff for the experienced plumbers out there, so if any of you can point me in the right direction, or suggest alternative approaches, I'd appreciate it!

Plumberboy

Simples!!!! Just add a tee piece to the mains water....Than run a new pipe to the existing tap........Put a valve on the new pipe that will now also be hooked up to the existing pipe so whenever theres no water turn on the valve manually and bobs your uncle!!!

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Plumberboy wrote: »

Simples!!!! Just add a tee piece to the mains water....Than run a new pipe to the existing tap........Put a valve on the new pipe that will now also be hooked up to the existing pipe so whenever theres no water turn on the valve manually and bobs your uncle!!!

Hmm.. that sounds straightforward enough, but doesn't it run the risk that if the rainwater comes back on again, the rainwater pump could backfeed rainwater into the other supply?

(A one-way valve would prevent this, but only until it failed, and you wouldn't know if it had failed.)

I think I'm really looking for a switchable valve that has two inputs and one output, such that you can have only one or the other selected at a time, with no way to have them both active.

Plumberboy

See what can be placed on the new pipe is a thing called a Non return valve, nothing can ever come back past the non return valve...Also you willl have a normal valve which can be opened manually which you can keep closed at all times until you are in the situation where you need to open it....

sullzz

Plumberboy wrote: »

nothing can ever come back past the non return valve..

non return valves often fail , you don't want to contaminate the drinking water supply with rainwater .

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Okay, I think I found the part I need: it's a 3-way ball valve, 'L' type:

One example is here: http://www.valfit.com.au/d58/b3210

Allows either left or right outlet to be connected to inflow, or neither, but not both. Perfect!

(Now I just need to find a local supplier that has them.)

tmcdlk

There is also the possibility of that valve leaking internally and the pressurised RW entering the mains supply. A simple solution is to have a quick release flexible pipe/hose setup.

You would have your RW and mains supplies side by side in the shed with a tap on each with hose tap connector. The pipe feeding your garden tap would have a flexible connection/hose with a quick release fitting on the end. Then it is only a mater of swapping the quick release fitting over to the supply you want to use.

So to switch from RW to mains you would close the isolation valve (or turn off the tap depending on how plumb it up), release the hose, swap it to the mains supply tap and open the isolation valve (or tap)

This will take slightly longer than turning a valve but it will guarantee that the mains won't get contaminated. You should use good quality brass hoselock fitting rather than the cheap plastic fitting.

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tmcdlk wrote:

There is also the possibility of that valve leaking internally and the pressurised RW entering the mains supply. A simple solution is to have a quick release flexible pipe/hose setup.

Thanks - hadn't realised ball valves could be prone to leaking also! Given that, isolating the connection does indeed seem the best solution.

Since the connection point would be in the plant area at the back of our utility room rather than outside, what's the best way to minimise spilt water during the swap-over?

Another possibility, of course, is that I give up on interconnecting them altogether, and just fit a second independent rear garden tap directly from the pressurised supply. This might be simpler all around, and I could use a simple bit of hose connector to connect the two adjacent garden taps together if I wanted to temporarily feed water to the tap out the front during dry periods.

(A one-way valve on the feed to the new garden tap would give some protection against the unlikely event that it was left turned on while temporarily connected to the rainwater system, and it then started to rain... It's likely to be driven off the pressurised house system rather than the mains water, both for plumbing convenience and also better pressure in the garden, so cross-contamination isn't quite as serious as it would be with mains, though still to be avoided.)

Micky Dolenz

You are over thinking the whole thing a bit I suspect.

Very low to zero risk of cross contamination where the worry is coming for a low pressure system into a high pressure one. The most likely outcome is high pressure system back filling rain water tanks and causing them to overflow.

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Micky Dolenz wrote: »

Very low to zero risk of cross contamination where the worry is coming for a low pressure system into a high pressure one. The most likely outcome is high pressure system back filling rain water tanks and causing them to overflow.

Hmm... good point. The rainwater system is pump-driven too, but I'm pretty sure it's lower pressure than our main house system which runs at around 2.9 bar.

LordSutch

Tenshot wrote: »

Hmm... good point. The rainwater system is pump-driven too, but I'm pretty sure it's lower pressure than our main house system which runs at around 2.9 bar.

Curous, what type of pump have you got? (Submersible 1000W maybe)? and how does it work re stopping when loft tank tank is full? and what bore of pipe did you use to connect pump to loft tank?

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LordSutch wrote: »

Curous, what type of pump have you got? (Submersible 1000W maybe)? and how does it work re stopping when loft tank tank is full? and what bore of pipe did you use to connect pump to loft tank?

We have Klargester's Envireau system, now Kingspan Environmental (http://www.kingspanwater.com/home-and-garden/index.htm).

There's a 6,000L tank buried in our front drive with a submerged pump and floating intake that feeds up to a dedicated attic buffer tank which then gravity-feeds the toilets. The pump shuts off automatically when water drops below a certain level (driven off a pressure sensor in the big tank connected to a separate control panel). I don't have the exact pump specs to hand but visually, it looks similar to the sort of 800W pump you might find in a modern apartment. Our garden taps are fed directly from the pumped output. The pipe up to the attic tank looks like 22mm; I didn't install it myself though.

The rainwater pump automatically turns on when system pressure drops below a certain point, i.e. when the ballcock in the attic tank opens to let more water in due to usage. If the rainwater tank is empty, then the pump doesn't run and so the attic tank slowly empties instead.

We moved in about two years ago and quickly decided that having an empty attic tank is no fun during dry periods, so we added a backup supply from mains. Essentially, there is a second, submerged float in the rainwater attic tank (not a ballcock; different sort of float) and if that float drops below a certain level, it opens the mains inlet to top-up the tank while maintaining the required air gap. It works pretty well, and ensures that our toilets don't notice when it hasn't rained for a while.

The plan was to have our washing machine running off the same attic tank, but our plumber decided to plumb that directly from the pump output instead :-( We didn't discover this until sometime later, which means the washing machine can run out of water; we ended up connecting it back to normal house water since it was too much hassle to keep switching over the pipes.

Otherwise, it works quite well. It's surprising how quickly you go through 6,000L of water though, especially when it hasn't rained for a while. (I saw a figure that at normal mains pressure, you can get through about 1,000L per hour just using a garden hose.)

LordSutch

Thanks for that, very informative & interesting. I am currently making a DIY system using whatever materials I can get my hands on, loft tank is already in situ, most of the piping is done, pump bought (Lidl 1100W submersible) which is probably overkill? but it should fill the loft tank pretty quickly (we also plan to introduce 'grey water' to the loft tank if rain water is insuficient) this will feed off the down pipe from the upstairs bathroom and collect in the same 600L tank in the garden, before being pumped back up to the loft tank where it will mix with the remaining rainwater - grey water will never be in short supply!

A few bits still to work out, like the electrics for the pump shut off, etc, but were getting there.

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LordSutch wrote: »

We also plan to introduce 'grey water' to the loft tank if rain water is insuficient) this will feed off the down pipe from the upstairs bathroom and collect in the same 600L tank in the garden.

Yes, if we were doing it all again, we'd definitely look at greywater recovery - between baths for the kids and power showers, I'm sure it would add up quickly.

600L is probably a bit on the small side for rainwater, but if you're supplementing it regularly with greywater, you should be fine! Presumably you won't be using it for the garden, only toilets? (Detergents etc in grey water won't do your lawn or plants much good.)

paddy147

Can I ask what is "greywater"

Is it the used water that comes from the washing machine and dishwasher??

How would you get the greywater to rise up into a water but/tank outside in the garden,instead of just going down the waste water pipe/gutter??

Thanks.:)

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paddy147 wrote: »

What is "greywater"? Is it the used water that comes from the washing machine and dishwasher?

Well, that's certainly I mean by greywater anyway - and Wikipedia agrees so it must be right :-)

How would you get the greywater to rise up into a water but/tank outside in the garden,instead of just going down the waste water pipe/gutter??

The trick there would be to take a feed from further up the drainpipe (which usually comes out the back or side of the house somewhere), above the level of the water butt, so that it can just feed in under gravity.

(Disclaimer: I'm not anything remotely resembling a plumber.)

LordSutch

Tenshot wrote: »

600L is probably a bit on the small side for rainwater, but if you're supplementing it regularly with greywater, you should be fine! Presumably you won't be using it for the garden, only toilets? (Detergents etc in grey water won't do your lawn or plants much good.)

WE only have one toilet in the house hance the smallish 600L external tank, and of course dont forget the 123L of storage in the new dedicated loft tank, which I installed specially for this project, this gives us 723L combined (all to flush one toilet). Re the Greywater; this will be specifically for flushing the toilet, and with ten or twelve flushes a day I'm sure our Rain/Greywater system will work like a dream. I might have to clean out the external tank once a year? but it will be sealed & vented. I might drop a cholorine tab in the tank every so often, just to help kill the bacteria

PS. I have another small 136L water butt ( with small 350W submersible pump) fed off the conservatory roof, this is dedicated to watering flower beds window boxes & the like . . . .

Solnskaya

The only legal solution is to have an air gap between the mains feed and the rainwater fed tank. You just have the mains pipe feeding in with a drop from the pipe outlet to the tank, should be easy to rig up with a ballcock and a simple stop valve. Anything else risks back syphoning and is barred. Should take all of oh, 30 minutes to rig up and bits would cost about €30.

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The only legal solution is to have an air gap between the mains feed and the rainwater fed tank.

Thanks Solnskaya. In this case, it's the pressurised house water system (taken from dual water tanks in the attic topped up from mains via an airgap) that would be used to supplement the rainwater feed so there is no risk of backfeed to the mains drinking supply, regardless of the final solution I end up with.

I hadn't thought of topping up the outside rainwater tank with mains. It would be a lot of work to get a mains feed to it, and would also effectively reduce the capacity of the tank by whatever top-up amount I set, but otherwise would probably work pretty well.

(The hose feeds are tee-d off the rainwater output before it makes it up to the attic rainwater storage tank, so topping up the attic tank doesn't get us anywhere - in fact we do that already from mains, via an airgap as suggested, but mainly to keep the toilets working during dry spells.)