Pipework between flow and return on cylinder/

[steveafoss]

Hi been to a property today when looking at vented cylinder noitced that there was a 22mm conection between the flow and return with a gate valve in between (gate valve was open) this was downstream of the pump. does anyone know why this would have been put in first time i have seen this. They dont have any problems with hot water but just wondered why this was here.

Cheers

 

[mcniven]

is that not a bypass

 

[Whn1]

Sure is...

 

[Howsie]

Gate fully open?

 

[mountainman]

Maybe the horse had already bolted!

 

[Guest123]

A good one I seen.....a gate valve fitted to the expansion pipe on a HWC!

 

[mcniven]

A good one I seen.....a gate valve fitted to the expansion pipe on a HWC!

Insane lol ..

 

[PlumbBobBob]

A good one I seen.....a gate valve fitted to the expansion pipe on a HWC!

perhaps it had been pumping over in the past and the "plumber" thought that would cure it

 

[mcniven]

Well he wasnt wrong Steveb!

 

[Guest123]

perhaps it had been pumping over in the past and the "plumber" thought that would cure it

....or kill it....and half the building if it was closed! LOL

 

[Nostrum]

I've seen check valves on the expansion before, when I asked who did it, the usual reply 'oh my dad's friend, he used to be a plumber' ... ok.

Later on in the week (full install) and running a new gas supply from a new meter to boiler 'we are thinking of putting a gas cooker in later on, can we just tee into that pipe' I replied 'yes you can', 'OK, great can you leave a tee piece in here so my dad's friend can run a new pipe in, he's got some of that plastic pipe in the garage........ I replied 'OK....'

who am I to say, the blokes a plumber after all..

 

[scotty plumber]

I once got told that if you have problems with air getting in to an open vented h/w system that you can fit a non-return valve on the end of the expansion pipe as long as you label it on the cylinder, does anybody disagree with this?

 

[Whn1]

I'm sure if you put a non return valve on the ov that could cause the cylinder to implode..

 

[Nostrum]

Possibly but in reality unlikely I suppose as the cold feed would still be clear? The expansion should be clear from obstruction along it's entire length though. It's a lot easier/safer to address the real cause of the air ingress rather than bodge it up with a non return valve!

 

[mikegas]

""...

 

[snowhead]

""...

+ ..... !

 

[steveafoss]

Hi been to a property today when looking at vented cylinder noitced that there was a 22mm conection between the flow and return with a gate valve in between (gate valve was open) this was downstream of the pump. does anyone know why this would have been put in first time i have seen this. They dont have any problems with hot water but just wondered why this was here.

Cheers

still not clear from replys why would you need a bypass on vented cylinder between flow and return am i being a bit thick

 

[Nostrum]

Ignore that doh not engaging my brain to the question!

 

[dontknowitall]

still not clear from replys why would you need a bypass on vented cylinder between flow and return am i being a bit thick

Safety. We all know that water expands 1600 times when it turns to steam.

If the boiler's heating the water and the circulation stops (eg trvs all close down, zone valve sticks, pump seizes, etc) the hot flow water cannot go anywhere and the boiler will continue to throw hot water into the system.

With the by-pass, the hot flow can, believe it or not(!), by-pass the rest of the system and return to the boiler by convection. Then the thermostat in the boiler will kick out to turn the boiler off before the water becomes hot enough to create steam.

(I occasionally ask for a quick poke around in customers' airing cupboards (so I can check on their underwe. ....OOOPS) so I can check for things like gate valves which must remain open or that there is a by-pass.) If I've turned up for a short job and finish in 5 minutes I can't justify £50 call out, but asking to look in the airing cupboard and explaining how the hot water cylinder works (most people have no idea!) this adds a few more minutes then their £50 seems more worth it.

 

[Best]

Joining the f & r pipes at cylinder is just a bypass. Stupid IMO. The gate valve is just to balance it. Usually the f & r are joined because a therm cylinder valve is fitted & will close the circuit obviously. Other method is the 3 connection therm valve which bypasses when valve shuts. Both ways help prevent pumping up likelihood, & keep flow through boiler. A proper bypass at boiler would be more sensible.