Feed and vent in an f and e system

[Johnyc86]

Hi plumbing experts
Can anyone tell me why a feed and vent are meant to be no more than 150mm apart as there teeing into system
Thanks in advance
Still learning the trade

 

[townfanjon]

Hi plumbing experts
Can anyone tell me why a feed and vent are meant to be no more than 150mm apart as there teeing into system
Thanks in advance
Still learning the trade

Its called close coupling and ensures most of the system is under positive pressure, its a must

 

[Johnyc86]

Its called close coupling and ensures most of the system is under positive pressure, its a must

If they were say 500mm apart on the flow what would happen then??

 

[Ric2013]

So that there is minimal resistance to flow between the two pipes. The pump pulls on the feed. If there were resistance between the two pipes, what do you think would happen at the vent?

Imagine a stopcock that is closed between the two pipes (that's even worse than a 500mm length of pipe) and I think you will guess what happens...

 

[Ric2013]

The pump is pulling on the cold feed (not exactly technically correct, but it will do for now) and pushing towards the vent pipe. There is an obstruction that prevents the water getting from the vent tee to the cold feed tee and thence on to the pump (your 500mm of pipe, or my hypothetical stopcock).

Where is the water going to go...

[EDIT - stayed online to see if you'd got there by now, but no reply from you so I'm going to bed]

 

[Roy_66]

Here's another thread with discussion of combined F & E (22mm min)

Combining feed and vent piping from F and E tank

It would save me a lot of faff if it was acceptable to combine the feed and vent in the manner shown in diagram below. Or should I resort to separate pipes for each, as small sketch. Boiler is Potterton Suprima I would be grateful for your advice. Thanks Rudy

www.plumbersforums.net

I also have a hazy memory somebody gave a link to where the F& E standards are all available on the internet? (Crook heights, pipe sizes, keeping pipes sloping etc.)

Cheers,

Roy

 

[Ric2013]

Hi

Here's another thread with discussion of combined F & E (22mm min)

Combining feed and vent piping from F and E tank

It would save me a lot of faff if it was acceptable to combine the feed and vent in the manner shown in diagram below. Or should I resort to separate pipes for each, as small sketch. Boiler is Potterton Suprima I would be grateful for your advice. Thanks Rudy

www.plumbersforums.net

I also have a hazy memory somebody gave a link to where the F& E standards are all available on the internet? (Crook heights, pipe sizes, keeping pipes sloping etc.)

Cheers,

Roy

Hi Roy. The OP is a student trying to understand 'close coupled' tees and why they 'MUST' be no more than 150mm apart, not trying to understand 'combined feed and vent' arrangements.

 

[Roy_66]

Hi

Hi Roy. The OP is a student trying to understand 'close coupled' tees and why they 'MUST' be no more than 150mm apart, not trying to understand 'combined feed and vent' arrangements.

Apologies Ric for bombing the thread, I just thought it might be an alternative solution if space tight etc (or whatever) to get the two pipes in. I do like simplicity, but take note of peoples reservations about single pipe systems.

 

[Ric2013]

Not a problem. Just trying to keep it simple for the lad who is presumably trying to answer a textbook question and stol