Re-using old pipe work for vent and cold feed

[baggielad]

I'm converting a gravity fed hot water to fully pumped but could someone confirm that it's ok to use the old cylinder flow and return pipes for the vent and cold water feed to the tank in the attic despite them both being 28mm. Thanks for any replies

 

[Terry lambert]

I would use just one of them extended in 22 up to the header tank in 22 as a combined feed and vent.

Basically a 22 cold feed, no vent required

 

[baggielad]

I would use just one of them extended in 22 up to the header tank in 22 as a combined feed and vent.

Basically a 22 cold feed, no vent required

Thanks for the reply. I thought that you had to have a separate vent and cold feed? I have the installation book for the boiler and it does show a separate cold feed and vet pipe and therefore should I just follow them and have separate pipes?

 

[swbjackson]

Some manufacturers will allow a combined feed and vent but not all so check the instructions carefully.

Nothing wrong with using the 28mm pipes as feed and vent, better that way than undersizing.

 

[Terry lambert]

As said, check with the manufacture.

I have never known a manufacture state that you can't do a combined feed and vent, but you live and learn.

It must be at least 22 mm .

This set up can also help you get out of problems on some installs like if you are pumping over or you have low head and you have limited options, or like in your instance it will save you running another pipe.

It's basically semi sealed, and is a handy option to be aware of

 

[twgas]

I always understood it as: IF the boiler HAS overheat protection you can use the combined feed and vent method, no overheat seperate feed and vent needed.

 

[Whitespirit66]

Ditto.

 

[Terry lambert]

Thanks twgas

Thanks for the info

 

[swbjackson]

Whilst working for eaga I had to go and alter a combine feed and vent to close couple because Vaillant had refused a warranty call as combine feed and vent wasn't shown as an approved configuration in the instructions.

If the instructions don't specifically allow for a combine feed and vent configuration I won't fit one to avoid warranty issues.

 

[Terry lambert]

It seems to me every time you phone tech you can get a different awnser depending on who you speak to.

I wonder if your experience would have been different if a different engineer had of attended?

I've spoken to their tech on issues and been told that the drawings are a "guide only, in terms that you might find in any plumbing book"

I don't know about that, but I do know I will be on the phone to them first thing Monday morning

 

[swbjackson]

That's trouble. If you get a Friday afternoon visit you'll get a different response from a Wednesday morning because the engineer wants to get home early. I won't deviate from the instruction manual unless I have something in writing from the manufacturer so that I can leave a copy with the customer.

If a boiler is suitable for use with a sealed system than it must surely be suitable for a combined feed and vent and you've eliminated any possibility of pumping over or drawing air down the vent.

 

[Terry lambert]

What's your question tutingay

 

[Dan Robinson]

Just taken 250000btu of boiler out of a room - all sitting on a solitary 22mm vent...

 

[Terry lambert]

Combined?

Aha.....but did it have overheat protection, and a fire extinguisher propped against the boiler doesn't count

 

[Dan Robinson]

Appliances were combined, but the vent and feed (22mm) pipes were separate. Although one boiler had an ISO valve on its vent (piccy in my album I think).


Worked for nearly 30 years but the HEXs were showing signs of the strain