Plastic overflow as prv discharge from unvented water heater?

[neiloneil]

I have fitted a ariston 15litre unvented water heater in an airing cupboard. A shower feed is situated fairly close to the unit, so I am opting to use the full range of expansion controls. Pressure reducing valve, Non return valve, expansion vessel, pressure relief valve, and tundish.
What I want to know is; Is it absolutely necessary for the prv to discharge through copper pipe?
The plastic overflow that is existing drops 1 meter straight down, then a shallow fall for another 2 meters where it connects to the kitchen waste outlet pipe The fitting guide says this pipe should be metal, but its going to be a problem getting a new pipe back to the kitchen or to an outside wall.

 

[Hot&Cold]

Good question but what does the ariston supplied literature say,ave a chat with them.

Every installation is different

 

[John D v2.0]

Is it absolutely necessary for the prv to discharge through copper pipe?

Yes, plastic melts easily, the water could be super heated water/steam under pressure, need hard metal piping run to a fall into a gulley or somewhere at low level outside.

 

[SandyLyon]

I have fitted a ariston 15litre unvented water heater in an airing cupboard. A shower feed is situated fairly close to the unit, so I am opting to use the full range of expansion controls. Pressure reducing valve, Non return valve, expansion vessel, pressure relief valve, and tundish.
What I want to know is; Is it absolutely necessary for the prv to discharge through copper pipe?
The plastic overflow that is existing drops 1 meter straight down, then a shallow fall for another 2 meters where it connects to the kitchen waste outlet pipe The fitting guide says this pipe should be metal, but its going to be a problem getting a new pipe back to the kitchen or to an outside wall.

Metal for a reason.

 

[FiremanT]

Yes, plastic melts easily, the water could be super heated water/steam under pressure, need hard metal piping run to a fall into a gulley or somewhere at low level outside.

Not saying you can use plastics, but it won't be under pressure after the tundish

 

[John D v2.0]

Not saying you can use plastics, but it won't be under pressure after the tundish

Didn't spot the tundish, thanks

 

[neiloneil]

Thanks for your comments. Because of a lack of route options for getting a 22mm copper pipe to an outside wall, I am now just considering getting a like for like replacement of a direct hot water cylinder and immersion heater. As it does not require a vent pipe, I can use the existing pipework.

 

[neiloneil]

Update..
I have returned the Ariston 15 litre water heater, and I am now shopping for a direct Fortic cylinder, as it has its own head tank , so venting or discharge is not an issue. I am thinking of an economy 7 type, as I only need the immersion element near the top, otherwise i will be heating up 100 + litres just for kitchen sink and hand basin. Can you suggest any other alternatives please?