HWC PRV/Ajax valve question...

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Jeeves

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# 177452 3-Aug-2015 10:32

Hidey ho,

So I was working in the garage over the weekend and whilst in there noticed water spewing over the edge of the roof on the house. It wasn't raining, so like any good kiwi I went into seek and destroy handyman mode.
My eyes advanced upward and saw the source of the sorcery - the HWC head pipe/overflow pipe.

I beckoned to the wife, and it turns out she was cleaning the upstairs shower, but mostly on cold water.

So our HWC is on the ground level, and the shower in question is on the first floor. This shower does suffer from low pressure on hot water.
I don't believe the HWC is mains pressure - probably medium pressure as I don't believe we have a header tank.

My question is - would one expect water to come out the header pipe when the shower mixer on the upstairs shower is set to anything but full hot water?

timmmay

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# 1357621 3-Aug-2015 10:38

I'm no plumber, but I would never expect water to come out of that pipe unless it was boiling and overflowing. How's your power bills looking? How about power consumption this month to date - you'd have to check your meter.

Bung

2901 posts

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# 1357627 3-Aug-2015 10:47

Your mixer is allowing high pressure water to backflow into the low pressure hot pipe.

Time to light the Bat signal and hope Aredwood notices 😃

richms

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# 1357657 3-Aug-2015 11:32

I got that with the old upstairs shower that just had 2 taps. Was damn hard to get it set to warm. Stopped when going mains pressure.

Richard rich.ms

DarthKermit

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# 1357825 3-Aug-2015 14:42

Gravity will work against you if you have a low pressure cylinder on the ground floor and an upstairs shower.

You can dial up the pressure on a pressure reduction valve, but be careful. Too high and it might burst the cylinder.

Jeeves

283 posts

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# 1358353 4-Aug-2015 09:15

Bung: Your mixer is allowing high pressure water to backflow into the low pressure hot pipe.

Time to light the Bat signal and hope Aredwood notices 😃

Hmm..sounds plausible. Will have to get up on the roof one day when i can be bothered and see if the water is hot/warm/cold...

Aredwood

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# 1359039 5-Aug-2015 00:32

Thanks Bung,
Most likely the OP has the wrong shower mixer installed. Or it was not adjusted / setup properly by the plumber who installed it. Turn the mixer to full hot - see how much flow you get. Then turn it to full cold and recheck the flow. The flow rates should be similar. If the cold water blasts out with heaps of flow / pressure. Then that is your problem - When the mixer is turned on with the handle in the middle - the cold water overpowers the hot. Which then causes water to shoot out the overflow pipe. Solution is to restrict just the cold flow. Or even better replace the mixer with one that has a venturi inside it. So the high pressure cold is used to help draw the hot water through.

Jeeves

283 posts

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# 1359092 5-Aug-2015 08:54

Thanks Aredwood - yea the mixer is a pain - when on cold it shoots out and when on hot it just dribbles out. Mixing it to get the right temp is a fine art - especially as we use it to shower the 18 month old so literally have to make mm adjustments to get the right temp. Will talk to a plumber.

richms

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# 1359160 5-Aug-2015 10:59

Seen crap mixers like that in several houses a friend has been looking at.

But in this property market with everything being an auction II can see why they do it all as the cheapest crap possible for sale. It just doesn't matter.

Richard rich.ms

Aredwood

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# 1359581 5-Aug-2015 18:01

Also could you measure the height difference between the mixer and the top of the hot water cylinder vent pipe. As in alot of houses like yours - cylinder downstairs. Bathroom upstairs. The best thing is often to bite the bullet and get mains pressure hot water. If your incoming water main is accessible. Install the limiting valve there. And you can have equal mains pressure hot water. Your mixer will then be really easy to adjust