Plumbers Help - Hot Water Cylinder - No pressure relief valve??

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samgdan

160 posts

Master Geek

#272080 8-Jun-2020 20:09

Hi,

I got a possible issue with a tundish dripping water. As far as I read it seems that I need to find the pressure relief valve and release some pressure (there is a process to do that and I found clear information about how to do it)

but I cant find the pressure relief valve. is it possible that a hot water tank does not have a pressure relief valve?

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3425 posts

Uber Geek

#2500900 8-Jun-2020 20:35

It's possible.
Your water cylinder is labelled low pressure so there should be little pressure to relieve.

I am guessing you don't have a header tank. Is that a pressure reduction valve where the cold comes in ?

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

samgdan

160 posts

Master Geek

#2500999 8-Jun-2020 21:00

the cylinder is located under the stairs, no header tank.

The only think I believe could be the pressure relief valve is what is pointing on the below photo.

but as far as I know the valve should be locate on the side nearly the top of the cylinder therefore I suspecting that no pressure relief valve is fitted?

if that is the case, what could be causing the dripping water on the tundish ?

elpenguino

3425 posts

Uber Geek

#2501004 8-Jun-2020 21:20

Not a plumber but a pressure reduction valve is to keep high pressure from damaging the cylinder. Therefore the valve is on the cold/input side of the system.

I can't see the lay of the land from the photos but does the thing you've arrowed leaf to the input?

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

JeremyNzl

359 posts

Ultimate Geek

#2501006 8-Jun-2020 21:22

Whilst I dont see a pressure relief valve, there is a pressure reducing valve and a low pressure cylinder.

This usually indicates an open vent pipe through the roof.

Your reducing valve is set to 7.5m of head and the vent pipe higher than that should not produce water except under a heating cycle.

samgdan

160 posts

Master Geek

#2501021 8-Jun-2020 21:58

elpenguino: Not a plumber but a pressure reduction valve is to keep high pressure from damaging the cylinder. Therefore the valve is on the cold/input side of the system.

I can't see the lay of the land from the photos but does the thing you've arrowed leaf to the input?

Yes it does go to the imput.

Thanks,

samgdan

160 posts

Master Geek

#2501023 8-Jun-2020 22:01

JeremyNzl:

Whilst I dont see a pressure relief valve, there is a pressure reducing valve and a low pressure cylinder.

This usually indicates an open vent pipe through the roof.

Your reducing valve is set to 7.5m of head and the vent pipe higher than that should not produce water except under a heating cycle.

no pipe to the roof as the cylinder is install under the stairs, however the water dripping on the tundish goes out to the back of the house.

it is more than dripping, water is flowing not a huge amount but it is just more than dripping.

thanks for the help.

Bung

6489 posts

Uber Geek

Subscriber

#2501041 9-Jun-2020 00:29

If you don't have an open vent there will be a pressure relief valve set to slightly over the reducing valve pressure òn the outlet of the tank. Any photos in your 1st post don't show for me.

PS I think the venting procedure you mention is for mains pressure tanks.

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nickb800

2719 posts

Uber Geek

Trusted

#2501087 9-Jun-2020 05:57

This diagram shows your low pressure system
https://www.hotwatercylinders.nz/images/source/Low_pressure_valve_vented.JPG

The pressure reducing valve (FV) is factory set so can't be adjusted. That suggests a leaky pressure reducing valve (RV). See if you can dismantle it to clean the seals (with water supply to cylinder turned off). Here are some diagrams which might help https://www.wattsnz.co.nz/products/plumbing-flow-control-solutions/relief-valves/pressure-only-relief-valves/rv-20-pressure-relief-valve

samgdan

160 posts

Master Geek

#2501105 9-Jun-2020 08:19

Bung: If you don't have an open vent there will be a pressure relief valve set to slightly over the reducing valve pressure òn the outlet of the tank. Any photos in your 1st post don't show for me.

PS I think the venting procedure you mention is for mains pressure tanks.

i was expecting that near the outlet (top of the cylinder) but i cant see it, what it is on the photos is what I have. this seems a bit weird as I reading everywhere that having a pressure relief valve a critical must have component of a water system.

Bung

6489 posts

Uber Geek

Subscriber

#2501148 9-Jun-2020 08:40

samgdan:
Hi,

I got a possible issue with a tundish dripping water. As far as I read it seems that I need to find the pressure relief valve and release some pressure (there is a process to do that and I found clear information about how to do it)

but I cant find the pressure relief valve. is it possible that a hot water tank does not have a pressure relief valve?

I just see place holder icons no images

samgdan

160 posts

Master Geek

#2501149 9-Jun-2020 08:43

Bung:
samgdan:

Hi,

I got a possible issue with a tundish dripping water. As far as I read it seems that I need to find the pressure relief valve and release some pressure (there is a process to do that and I found clear information about how to do it)

but I cant find the pressure relief valve. is it possible that a hot water tank does not have a pressure relief valve?

I just see place holder icons no images

ok I uploaded the photos correctly, maybe issues with your browser?
thanks for the help

nickb800

2719 posts

Uber Geek

Trusted

#2501153 9-Jun-2020 08:55

samgdan:

Bung: If you don't have an open vent there will be a pressure relief valve set to slightly over the reducing valve pressure òn the outlet of the tank. Any photos in your 1st post don't show for me.

PS I think the venting procedure you mention is for mains pressure tanks.

i was expecting that near the outlet (top of the cylinder) but i cant see it, what it is on the photos is what I have. this seems a bit weird as I reading everywhere that having a pressure relief valve a critical must have component of a water system.

Please read my message above. Your cylinder has two pressure reducing devices, but because it is low pressure, it doesn't have one on the top of the cylinder with a lever to relieve pressure.

samgdan

160 posts

Master Geek

#2501210 9-Jun-2020 09:29

this has to be the one, correct? do you know the procedure to relief some pressure if that is the pressure relief valve?

Thanks,

nickb800

2719 posts

Uber Geek

Trusted

#2501228 9-Jun-2020 10:02

Yes, that's the pressure reducing valve which is likely causing your leak (the brass thing above the black plastic tundish). You can't relieve the pressure with this type (mains pressure type valves have a lever to relieve pressure, that's probably what you've read about). Your only option is to dismantle it, clean the seals and hope it works when you put it back together. It may need replacing.

samgdan

160 posts

Master Geek

#2501234 9-Jun-2020 10:14

nickb800:

Yes, that's the pressure reducing valve which is likely causing your leak (the brass thing above the black plastic tundish). You can't relieve the pressure with this type (mains pressure type valves have a lever to relieve pressure, that's probably what you've read about). Your only option is to dismantle it, clean the seals and hope it works when you put it back together. It may need replacing.

Thanks for your reply. I might try that. looks like the link you sent me is the correct one. however I will try to get as much info as I can so I can get some pricing.

I guessing to replace that valve the procedure would be something like, empty the cylinder, turn off the power, remove, clean/replace if needed.

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