Roof Mounted Relief valve

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aussiedean

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#316098 16-Sep-2024 15:33

Hi all,

Asking on behalf of my parents place in West Auckland. As you can see from the photos the Relief valve if it is that on the roof has been leaking for a bit. Mainly seems to be though when
you turn on the hot and cold water taps together it shoots out a stream of water probably 3 mrts across the roof.

Obviously something is wrong here like the valve will need replacing. But could someone explain what that might be, its not just a drip when the pressure gets too much it fires out quite a bit of water
when say you want to fill a basin and both taps are turned on at once.

Any recommendations for a good plumber in West Auckland area that would be a reasonable price for pensioners?

Bung

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#3282688 16-Sep-2024 15:56

Are they separate taps connected to a single outlet or a mixer tap. What you appear to have is mains pressure cold and lower pressure hot. The cold water is backfeeding high pressure water to the hot water tank which is then venting onto the roof. If may be possible to restrict the cold flow to stop this happening.

DonH

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#3282701 16-Sep-2024 16:19

That's weird. It looks a little like an Ajax valve but it won't do any good mounted there.

An Ajax (brand name) valve is a pressure operated valve that is fitted in the inlet pipe to the bottom of the hot water cylinder. The pipe on the roof is attached to the top of the cylinder. The cylinder fills with water and it starts to rise up the pipe. As it rises, the water pressure as seen by the valve increases, causing the valve to close. There's an adjustment on the valve to set the shut-off pressure, and thus the hot water pressure.

The usual failure mode is that it starts to leak internally, resulting in a steady dribble of water from the roof pipe. Your symptoms sound different. Either the valve is sticking open when water is run, or there is some type of internal path in the house from the cold water to the hot water pipes, maybe a defective mixer tap. Either way, it's definitely a job for a plumber.

Also see this thread:
https://www.geekzone.co.nz/forums.asp?forumid=141&topicid=177452

People hear what they see. - Doris Day

tweake

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#3282702 16-Sep-2024 16:19

the other thing is that its a 20 year old cylinder thats probably on its last legs.

you may want to consider upgrading the system to mains pressure.

aussiedean

65 posts

Master Geek
+1 received by user: 1

#3282704 16-Sep-2024 16:39

Thanks Bung for the quick reply, there are no mixer taps in the house and the house is like 60 years old. There is an Ajax valve underneath the house too

aussiedean

65 posts

Master Geek
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#3282705 16-Sep-2024 16:42

Thanks Tweake ... yep agree the age is getting up there and I would probably put in a new system if mine.

aussiedean

65 posts

Master Geek
+1 received by user: 1

#3282706 16-Sep-2024 16:45

Thanks DonH for the explanation, I agree I plumber job for sure. Personally I have a different setup in Australia where I live. Anyway will get a plumber around for a look and go from there.

Thanks all ...thats very helpful

Dell

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tweake

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#3282712 16-Sep-2024 17:24

DonH:

That's weird. It looks a little like an Ajax valve but it won't do any good mounted there.

its a pressure valve used to increase the hot water pressure. seams to be an old school trick which i'm told is illegal. i had the same setup done on mine.

Bung

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#3282714 16-Sep-2024 17:29

aussiedean:
Thanks Bung for the quick reply, there are no mixer taps in the house and the house is like 60 years old. There is an Ajax valve underneath the house too

Is there a shower? That's the sort of 2 into 1 outlet that allows back feeding.

The valve on the roof is not an Ajax but a relief valve with a rating just higher than the Ajax setting. Adding it to an existing vent tube is a bit of a hack to get more pressure.

kotuku4

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#3282726 16-Sep-2024 18:32

tweake:
the other thing is that its a 20 year old cylinder thats probably on its last legs.

you may want to consider upgrading the system to mains pressure.

The existing is mains pressure at 12m. Low would be 7.6m pressure max.

caffynz

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#3282732 16-Sep-2024 18:55

aussiedean:

Thanks DonH for the explanation, I agree I plumber job for sure. Personally I have a different setup in Australia where I live. Anyway will get a plumber around for a look and go from there.

Thanks all ...thats very helpful

If still looking for plumbers in West Auckland, try Proline Plumbing & Gas, I've used them and found Ross very good at explaining the issues/situation and my options.

Bung

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#3282735 16-Sep-2024 19:08

kotuku4:

The existing is mains pressure at 12m. Low would be 7.6m pressure max.

12m or 120kPa is still regarded as low pressure although it is streets ahead of the lower options. Mains pressure is typically 350 - 700kPa

Dell

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aussiedean

65 posts

Master Geek
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#3282854 16-Sep-2024 21:46

Thankyou all so much, appreciated greatly
with the in depth explanations.

Will pass on and hopefully get it sorted soon.