f&e quandry

[skier1]

I'm tidying up my loft and taking the opportunity to renew my cold water and f&e tank. The cold tank is not much of an issue but I am puzzled by the f&e tank, it currently has a vent coming from the exit below the tank, rising to 1 m above the tank before dropping down above the water level > My original question was 'why is the vent so high?' but thinking about it, why have a vent at all as the tank is open to the atmosphere ?
Thinking further, it seems an unnecessary complication to feed the f&e tank via a ball valve. This is only useful when topping up after a rad change. This could simply be replaced by a manual valve, this would be much safer and would eliminate the possibility of leaks being mains fed. Sorry this is so long but I'm genuinely puzzled by these two issues.

 

[rocketmanbkk]

I think you need to consult a plumber pal as you clearly have no idea as to why things are as they are

There's a reason for the vent pipe & its height & also the ball cock.

Good luck

 

[Last Plumber]

I'm tidying up my loft and taking the opportunity to renew my cold water and f&e tank. The cold tank is not much of an issue but I am puzzled by the f&e tank, it currently has a vent coming from the exit below the tank, rising to 1 m above the tank before dropping down above the water level > My original question was 'why is the vent so high?' but thinking about it, why have a vent at all as the tank is open to the atmosphere ?
Thinking further, it seems an unnecessary complication to feed the f&e tank via a ball valve. This is only useful when topping up after a rad change. This could simply be replaced by a manual valve, this would be much safer and would eliminate the possibility of leaks being mains fed. Sorry this is so long but I'm genuinely puzzled by these two issues.

Don't be tempted to block the vent. It could be very dangerous.

It needs to be there and there's possibly a good reason why it is so high.

The ball valve is there to maintain the water level. So you don't have to remember !

 

[rpm]

What do you think the letters F&E refer too? Learn this and you will see why it is like it is.

 

[SimonG]

Or get a g3 plumber to check your water pressures and flows, that your boiler can run on a sealed system and go sealed and unvented.

Then you won't need to replace the tank or do any tidying 🙂

 

[skier1]

Are you not a plumber then ?

 

[skier1]

What do you think the letters F&E refer too? Learn this and you will see why it is like it is.

Thanks for not helping

 

[skier1]

I think you need to consult a plumber pal as you clearly have no idea as to why things are as they are

There's a reason for the vent pipe & its height & also the ball cock.

Good luck

Yes, thanks, hence the question. Are you not a plumber? Are you able to give the reason?
I understand that the ball cock is a convenience but only when you change part of the system. If you have a leak, say under the floor, then the ballcock will ensure maximum water damage by feeding the leak for ever, and ever

 

[skier1]

Don't be tempted to block the vent. It could be very dangerous.

It needs to be there and there's possibly a good reason why it is so high.

The ball valve is there to maintain the water level. So you don't have to remember !

Thanks, the vent comes from the pipe exiting the bottom of the tank. The water level in the vent will always be at the same level as the water in the tank so it serves no purpose.
The ball valve would feed a system leak, say while you are away. For the limited times it's needed it seem an unnecessary risk.

 

[SimonG]

Engineer?

 

[SimonG]

Thanks for not helping

It was good advice.

Yet again we are forced on the muppet train.

If you don't want to listen to advice, why ask?

Reminds me of my kids when they were younger.

 

[steadyon]

F&E stands for feed and expansion.

The tank feeds replenishment water to the boiler. Replenishment is rarely needed in any volume, but most systems lose some water through micro-leaks etc. If the boiler is allowed to run dry, the results will be, to say the least, expensive. Hence the use of a float operated valve to replenish the supply. It will, as you say, continue to feed any underfloor leak, but this may be preferable to a ruined boiler.

The expansion pipe accommodates the 4% increase in the volume of a body of water heated from 0 to 100 degrees Celsius. It is normally a 22mm pipe with a minimum height above the water level in the F&E tank of 450mm (from memory, might be 300mm), and must have no valves or other stoppages, and should rise continuously, between the boiler and the end of the expansion pipe. The pipework to feed water to the boiler is normally 15mm, may have valves in it (although normally open) and may not be able to accommodate a sudden expansion of volume, for example in the event of a boiler malfunction.

In summary, the float operated valve prevents the boiler being damaged, and the full sized expansion pipe prevents you being damaged.

 

[rpm]

Thanks for not helping

But I am, my apprentices are taught to research things then I`m there to guide them, this way things stick better in their pea brained head.

 

[SimonG]

Quick lesson on thermodynamics.

Water expands by 4% when heated.

The water in your central heating system needs somewhere to go once heated. Hence feed & E X P A N S I O N tank.

Your boiler stat or high limit stat fails and boils your water. It will enter the F E E D & E X P A N S I O N tank rapidly. Exiting the overflow.

You will have general water losses. Normally called E V A P O R A T I O N. Which is where the F E E D part of the F E E D & E X P A N S I O N tank.

If you don't like, then you have been given options. Even could swap to a sealed system if your boiler is suitable.

The real problem you may have however, is that your poor attitude will mean you will either struggle to find somebody to do the job or you will pay over odds by way of addition of the idiot tax.

But hey, everyday is a school day 🙂

 

[Last Plumber]

Quick lesson on thermodynamics.

Water expands by 4% when heated.

The water in your central heating system needs somewhere to go once heated. Hence feed & E X P A N S I O N tank.

Your boiler stat or high limit stat fails and boils your water. It will enter the F E E D & E X P A N S I O N tank rapidly. Exiting the overflow.

You will have general water losses. Normally called E V A P O R A T I O N. Which is where the F E E D part of the F E E D & E X P A N S I O N tank.

If you don't like, then you have been given options. Even could swap to a sealed system if your boiler is suitable.

The real problem you may have however, is that your poor attitude will mean you will either struggle to find somebody to do the job or you will pay over odds by way of addition of the idiot tax.

But hey, everyday is a school day 🙂

Couldn't have put it better myself !

 

[mache]

I'm just going to play devils advocate here.
Certainly the query regarding the float valve is at best nieve, however if I understand the vent pipe question then I read it that the vent is not directly from the main boiler outflow piping, but is tee'd off from the feed and expansion tank directly below said tank. If that is the case then I fully understand why he would question the need for the vent. So actually OP should have asked 'it looks like the vent pipe on my central heating has been tee'd off from the feed and expansion pipe.. is this correct as it appears to serve no additional purpose.'
Now not being a plumber myself it doesn't sound right to me.

 

[Last Plumber]

You're right it's not.
The OP has presumed that it is pointless rather than thinking it may have been incorrectly installed. However, it seems he is unwilling to listen

 

[Best]

Thanks, the vent comes from the pipe exiting the bottom of the tank. The water level in the vent will always be at the same level as the water in the tank so it serves no purpose.
The ball valve would feed a system leak, say while you are away. For the limited times it's needed it seem an unnecessary risk.

You have no idea about the purpose of the vent. Here is a bit of education for you, - the vent pipe is for the purpose of a vent and expansion. The water does not always stay at same level as in expansion tank when the heating needs to expand, or is overheating. Do you understand capillary action? Similar thinking.
If you do away with the vent, then you will not only just be depending on the feed pipe as a sole feed and vent, but you will introduce corrosion problems and air.
The Ballvalve is required for slight top ups, but if you want you could turn the mains off and on to the f&e tank or get the system sealed if possible.
If ballvalves and vent pipes were not needed, then we would have figured that out and be glad to not bother installing them.

 

[mache]

it currently has a vent coming from the exit below the tank, rising to 1 m above the tank before dropping down above the water level

OP can you post a picture of the piping of the tank and the vent?
If your vent pipe is joined to the pipe exiting the F&E tank then this sounds like an original installation error.

 

[Stigster]

I have a vague memory of some kind of combined feed/vent system being used under certain circumstances. Sorry this is so vague and I'm not saying what OP has is right at all but does anyone know what I'm talking about?

Edit - Like this in post No. 4 on this forum Ask The Trades - Vent pipe siziing