gate valve and vent on header tank outlet to speed future work

[John stafford]

Hi,
about to replace some radiators, so need to drain system.
While i'm doing it I'm thinking about doing a mod to make future drain downs quicker:
Idea is adding a gatevalve on header tank outlet, and just below the gatevalve add a tee to a pipe that goes up to above tank level with another gate valve on that pipe (air admittance pipe).
Normally tank outlet valve will be open, and one on other pipe will be closed.
Then to drain system, close header tank outlet valve, and open air admittance pipe gatevalve. then only need to drain volume of water in pipework to do work.
What do you experts think of this ?
thanks John

 

[ShaunCorbs]

Just put a valve on the supply feeding the tank eg cold water mains

 

[John stafford]

yeah, but then I would have to drain the header tank each time, which is several gallons, through a slow drain outlet.

 

[ShaunCorbs]

yeah, but then I would have to drain the header tank each time, which is several gallons, through a slow drain outlet.

Shouldn't be gallons max 4 litres

Also drain valve should be full flow washer stuck ??

 

[Chuck]

yeah, but then I would have to drain the header tank each time, which is several gallons, through a slow drain outlet.

Just stick a bung in the outlet.

Avoid draining the contents of a F/E tank down through the system if you can. It'll probably be full of sludge, which is better siphoned or wet-vac'ed out.

 

[Best]

A feed pipe from heating tank (f&e tank) is also a safety vent and should never have any valve on it.
Only should have an isolating valve on mains supply to ballvalve.
Gatevalves should be avoided anyhow as they tend to seize, break, or not seal off fully.
F&E tanks are called 10 gallon/4 gallon because they are supposed to only hold maximum of 4 gallons and be for top up and expansion, not storage.
If your tank has much more than about 3 inches depth of water, then it is wrong and needs that sorted.

Your problem with “slow drain” is caused by not having a good drain point . Use a full flow valve on lowest point of system to aid fast draining. Also fit a stopend on it to prevent it being opened accidentally.

 

[Ric2013]

Exactly as Shaun has said, but in more words:

In nearly every domestic system, the water level in the F&E serving the primary circuit (boiler and rads) should be as low as possible. In practice, the valve is usually installed quite high up the wall of the cistern and the water volume is higher than is strictly needed. Sometimes a BS1212: part 1 ('Portsmouth') valve can be replaced with a part 2 to lower the water level, or the float arm can be carefully bent down.

Drain valves are often very poor (because householders don't tend to use and notice them and so they are built to a cost), especially once they are old. Often the washer goes hard and seizes onto the seat and you find the water is only draining through the hole in the middle of the washer. If draining remains slow after rectifying, you may find the tank outlet itself is partially obstructed (look up 'blocked feed from F&E').

 

[John stafford]

Thanks for advice, going to drain tomorrow, already found several drain cocks need replacing as having opened them they now leak. I guess I can just replace the unscrewable bits of soldered valves, others are 1/2" bsp so can easily fit new complete valves.

 

[Ric2013]

Thanks for advice, going to drain tomorrow, already found several drain cocks need replacing as having opened them they now leak. I guess I can just replace the unscrewable bits of soldered valves, others are 1/2" bsp so can easily fit new complete valves.

Probably just clean out the dirt and remnants of old washers and fit new washers. I nearly always replace draw-off cock washers whenever I drain down: saves hassle later.

 

[John stafford]

Do all 15mm / 1/2" bsp drain cocks use the same washers?

Having drained completely today, I can see not draining header tank really wouldn't save much time. The bulk of the water drains very fast, it's the last little bit in each rad drop that takes the time.

 

[Ric2013]

Do all 15mm / 1/2" bsp drain cocks use the same washers?

Having drained completely today, I can see not draining header tank really wouldn't save much time. The bulk of the water drains very fast, it's the last little bit in each rad drop that takes the time.

You get the type A and type B washers, but other than that, they tend to be fairly standard. Some merchants will sell you a mixed bag.