Heat loss from vent pipe

[duffsparky]

My central heating has broken down and I can't afford to fix it coz I'm going through a divorce. I'm using the immersion heater for dHW but it gets cold very quickly; this is probably due to the rest of the house being only 2 or 3 degrees above the ambient outside temperature (sometimes it's warmer in the fridge than in the kitchen brrrrrrrrrr- no bull, I'm monitoring the pipework temp so I can drain it should it get cold enough to freeze). The tank is a fairly modern pre-lagged one covered in yellow polyurethane(?) foam; so I'm guessing that, as there are no leaks I can find, the heat loss is via thermal convection up the vent pipe.

I seem to remember quite some time ago reading an article about connecting the vent pipe of a HW cylinder below the level of the cylinder outlet to prevent gravity heat circulation but I can't find that article any more or any other like it. See drawing below

Has anyone got any advice on this?

Thanks.

 

[REDSAW]

might not help,
get a hot water bottle and a few fan heaters cheap.

why not leave the immersion on as it will keep the water temp topped up as you are saving on gas then it will cost no more?.

 

[Mike Jackson]

Don't do it. The open vent from a vented hot water storage cylinder should rise continually. In the layout you've pictured it is possible to rupture the hot water cylinder in the event of an immersion heater failure. Particularly in the cold weather.

Just imagine, the gate valve is turned off or the cold feed to the cylinder freezes. You turn on a hot tap and not much comes out but enough to create an airlock in the dropped section of pipe. You turn the hot tap off again. The immersion stat fails and the water boils in the cylinder, an air lock will hold back a considerable pressure so the pressure will rise in the cylinder until it ruptures.

It may sound a bit far fetched but I've had a cylinder collapse due to an airlock in an incorrect open vent when I tried to drain it.

The pipe layout you're thinking of is for use with an unvented cylinder.

 

[PlumbBobBob]

besides which you could get an airlock where the pipe goes up then down

 

[duffsparky]

might not help,
get a hot water bottle and a few fan heaters cheap.

why not leave the immersion on as it will keep the water temp topped up as you are saving on gas then it will cost no more?.

I'm trying to cut my expenditure to an absolute minimum coz I'm unfortunately also out of work (business failed and can't get a job) so running the I/H all the time seems a tad excessive. I've got a convector heater which I keep in one room and live in there as much as possible, admittedly not ideal but it'll do for a while.

Don't do it. The open vent from a vented hot water storage cylinder should rise continually. In the layout you've pictured it is possible to rupture the hot water cylinder in the event of an immersion heater failure. Particularly in the cold weather. ..........................
The pipe layout you're thinking of is for use with an unvented cylinder.

I take your point Mike although trying to understand the mechanics behind it is a bit difficult coz I'd have thought the outgassing and pressure build up from the runaway I/H would have been sufficient to overcome any airlock and release up the vent pipe, that is, unless the drop pipe is excessively long. Anyway I bow to you greater knowledge.

I've just thought of another problem but I'll start another topic for that and link back to this one.

 

[Best]

Never heard that said before! Seen a lot done like that due to bad work, without reason. Probably would stay like that for years, but is risking problems.
The cylinder will gather air, which will then keep the taps spluttering when first opening a tap. The vent is there for a purpose.

 

[Best]

Should have said that the cheapest, less wasteful way of electrically heating a small amount of water, is use a kettle! Dangerous though to carry it anywhere without mixing cold water with it.
I know a guy heats his water this method!

 

[Mike Jackson]

Never heard that said before! Seen a lot done like that due to bad work, without reason. Probably would stay like that for years, but is risking problems.
The cylinder will gather air, which will then keep the taps spluttering when first opening a tap. The vent is there for a purpose.

A neighbour of my parents had a cylinder burst due to the cold feed and open vent freezing. Not too far from this scenario.

 

[duffsparky]

I'm probably gonna leave the system as is for now but would installing a surrey, york or similar outlet flange with automatic air vent and pressure release valve overcome the problems mentioned above ie accumulation of air in top of cylinder, airlock and bursting tank?

 

[tamz]

The heat loss through your vent pipe is minimal. The heat only travels a couple of feet at most from the cylinder when you are not drawing water. Buy a few lengths of lagging and lag all your hot pipes nor if you can't afford lagging use anything, old clothes, the ex wife's fur coat, old blankets, whatever is lying around.

If your name is any relation to your trade put your skills to greater use.
I'd tell you one thing, if it was me i wouldn't be sitting in the cold. I'd have the house like Blackpool illuminations and have to open the back door to get a breath of air.

 

[Mike Jackson]

I'm probably gonna leave the system as is for now but would installing a surrey, york or similar outlet flange with automatic air vent and pressure release valve overcome the problems mentioned above ie accumulation of air in top of cylinder, airlock and bursting tank?

All you need to do is ensure that the vent rises all the way to the CWSC. A horizontal section isn't too bad. The only time you really need to worry with air accumulating with a correctly installed system is if you start adding pumps, then you need to start thinking about adding flanges, my preference is for a Warix flange.

 

[WaterTight]

Are you near a gym? Ever fancied getting fit? Some gyms are quite cheap especially if you have a non-peak times memberships. Some are £20-£30 a month. And you can have a long hot shower every morning. Possibly even a swim and a jacuzzi. Cheaper than altering your plumbing or boiling kettles for baths.

 

[Plumbus]

I would install a cheap electric shower....or go to swimming pool as a visitor and 'pop in' to the shower!!!