Combined F&E pipe problems

[WHPES]

I have yet again come across a problem with a central heating circuit in my local area. Some time ago, probably in the 70s and 80s, a local tradesman decided that he only needed one pipe from the F&E cistern, and this would tee into the pipework immediately above the coil on the hot water cylinder (usually the shortest distance possible). About 2 inches from the outlet at the base of the F&E tank, he teed in a swan neck which came over the top of the tank in the way you would expect to find a vent pipe.

Obviously the systems like this are a complete nightmare. They take ages to fill as the feed water is competing with the air which is trying to get out of the same pipe, the system can take weeks to get rid of all the air, and they are prone to blockages where the pipe tees into the circuit, on one occasion building up so much pressure it popped a joint, which could be potentially dangerous. There are literally dozens of houses round here plumbed up this way.

On some occasions there is a separate vent pipe but it is only teed into the circuit next to the feed pipe.

Does anyone on the forum come across this arrangement or is it just in my area? The usual fix I do is add a proper vent pipe and move the feed pipe to near the boiler. Where I can't do this, I convert to an unvented system.

 

[WOLDEN]

i was taught by a exp B G man , if you have a blocked cold feed , you can use open vent pipe , as long as the boiler has a over heat stat fitted. also stops heating from pumping over .

 

[Plucky]

Quite comman and not alot wrong with it in my opinion as you say take longer to fill and vent.

 

[justlead1]

Hi. Its not local to your area. If i recall correctly it was introduced about the same time as the transition from gravity F&R to pumped primaries. The conventional method at the time was cold feed to boiler/return and vent of highest point of gravity flow. But as you will be aware, this set up pumps over when a circulatory is fitted. People like Servowarm (a national outfit) used a similar set up, probably forced pressure to bear on standards. To sell more systems, sell more gas,save copper and make systems easier to install(deskill) as first generation combi. Coal was also getting political at the time. If required to drain such a system always filled with a hose to a drain cock, watching overflow pipe to determine when to vent rads. (not a double check valve in sight) Good Luck

 

[WHPES]

i was taught by a exp B G man , if you have a blocked cold feed , you can use open vent pipe , as long as the boiler has a over heat stat fitted. also stops heating from pumping over .

There is a SINGLE pipe from the F&E. there is NO dedicated vent pipe. If the pipe gets blocked and the water expands, the system effectively becomes pressurised and a joint will blow apart or a pipe will split.

 

[Plucky]

There is a SINGLE pipe from the F&E. there is NO dedicated vent pipe. If the pipe gets blocked and the water expands, the system effectively becomes pressurised and a joint will blow apart or a pipe will split.

What he is saying is that an old blocked feed would be cut off or capped and the existing vent would be utilised as a combined feed and vent.