Hot or Cold water to outside tap


I have an outside tap, currently fed from the mains. I have a combi-boiler. I want to be able to switch between hot and cold water to the outside tap. I don't want to actually mix the hot and cold - I just want to electrically switch between the two supplies to the tap.
Ideas?
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On Tue, 27 Oct 2015 09:24:22 +0000, John wrote:

Instant water heater on the inside of the wall, and a power switch for it next to the tap?
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Why electrically? It would no doubt be possible but it would seem to add a lot of complications.
Why not just use a three way valve? Like this maybe?
http://www.ebay.co.uk/itm/like/291536406284?
Tim
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On 27/10/15 09:42, Tim+ wrote:

If he buys the rest of that valve (a standard 3 port) he'll be able to do it electrically :)
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It's not suitable for mains pressure use, and needs the water to enter the common port.
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The pipes and any tap/valves on the inside will be in quite an inaccessible place for day to day access.
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On 27/10/2015 13:28, John wrote:

As I said earlier, tee off the hot supply and run the pipe to another outside tap next to the cold one (if poss). The new outside tap will have a NR Valve fitted integrally. No electrics involved.
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On 27/10/15 13:28, John wrote:

Pair of single valves would be better then IMHO - both off for winter.
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I think that is the way I am going to go. Thanks to you and all others with their comments and suggestions.
I have looked at motorised valves - and it would seem that there is a danger of them "wearing" out. I think I would like to try a simple solenoid type valve - which is only activated when needed. So - normally closed - apply the power and the solenoid opens. I am guessing that these are different from "motorised" valves which appear to have limited life and a finer adjustment (not just on or off) : or is it just a different name for the same thing?
Any further suggestions/comments on solenoid valves would be appreciated.
(PS I am not actually going to DIY it - I am looking for ideas/components which I can discuss with a professional when I am ready to go)
Again: thanks to all for comments - appreciated.
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A motorised valve only takes current while it operates - moves from open to closed or the reverse.
A true solenoid valve would need power all the time it was in one state, or some form of latch mechanism to hold it after it's moved.
Think central locking in a car. At one time this did use solenoids. But these days invariably motors.
Motors are also more efficient than solenoids.
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wrote:

Nope, my Hyundai has solenoids, very characteristic sound when they operate and that’s what the manual says too.

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Of course - outdated technology. Like all these bargain basement makes.
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On 28/10/2015 11:13, Dave Plowman (News) wrote:

Not generally true for the sort used in heating systems. They have a spring return and close as soon as power is removed. To keep them open, the motor needs to be continuously powered - and simply stalls.

Since the OP wants to feed an outside tap, that will presumably only use water for short periods, so requiring continuous power during 'on' periods shouldn't be a problem.
CH-type motorised valves are not designed for mains pressure, whereas the solenoid valves used on washing machine inlets *are*. A couple of these from a scrap hot & cold fill washing machine would probably do the job as long as you can find a way of connecting them. The ones I've seen have a 3/4" male BSP thread on the inlet side - which is easy to connect to - but the outlet side feeds into a chamber, so it would be necessary to make a housing of some sort with a pipe connector on *its* outlet in order to use the valves in an in-line situation.
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On 28/10/2015 20:27, Roger Mills wrote:

http://cpc.farnell.com/unbranded/71-un-58/solenoid-valve-1-way-180-degree/dp/WG22218
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On 28/10/2015 20:27, Roger Mills wrote:

http://cpc.farnell.com/adafruit-industries/997/solenoid-valve-plastic-water-12v/dp/SW04771?MER=e-bb45-00001003 if 8 bar is enough, I assume they mean mega pascals and not milli pascals.
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On 28/10/15 20:27, Roger Mills wrote:

It's also not true, in the common case of spring-return motorised valves.
I agree, having checked, that CH valves are no good as one quotes a max differential pressure of 0.7bar
However:
http://www.ebay.co.uk/bhp/electric-water-valve
Lists quite a few and one is fine up to 9.8bar.
The other question is: does the OP care if the valve is approved for potable water?
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John wrote:

Possible the cheapest source of electrically controlled valves would be from a scrap washing machine.
You should probably also make sure you fit non-return valves to prevent any chance of back-flow.
Chris
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Is that possible with a combi?
Tim
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Tim+ wrote:

Possibly not but water regs will want a NRV on the outlet or if easier on both feeds.
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But with no storage tank, it makes no sense at all. Not saying that you're wrong but who is going to come out and check for NRVs? ;-)
Tim
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