Vents on water tank take offs ???

[quattro64]

Hi Everyone

Wonder if someone can help me.

I have to replace a couple of 250g tanks and some pipework in an old London block of flats.
the tanks are 6 floors up and feed the flats below,
Comming out of the tanks are 2 x 1 1/4" pipes that have stopcocks on them and they then go down to feed the flats below.
Immediately before the stopcocks are what I can only describe as some sort of vent.
There is a 1/2" pipe rising vertical to above the water level in the tanks and then doubling back on itself and left open.
Can someone tell me what they are there for and do they need re-instating when I replace the pipe work?
I am sorry if this is a bit of numpty question but i have never seen anything like it before.
Many thanks in advance.

 

[chris watkins]

Just air vents & no, unless new /old pipework will trap air.

 

[quattro64]

Many thanks Chris
Out of interest, was it normal to install them at some time in the past?
Where they are currently positioned there would have been no problem with trapped air because of the fall on the pipes.
Cheers

 

[deadstare]

Being an older system it Sounds like they may have had a problem with air locks in the past

 

[chris watkins]

Many thanks Chris
Out of interest, was it normal to install them at some time in the past?
Where they are currently positioned there would have been no problem with trapped air because of the fall on the pipes.
Cheers

Not normal but have seen from time to time (even older than me) not sure total why it was done, as far as I could work out it was in a time before AAV's, so have seen on long runs through lofts. On your one it may have been because they wanted to keep it open to atmosphere to speed draining or filling, is there a manifold or isolation on each drop ?

 

[quattro64]

Not normal but have seen from time to time (even older than me) not sure total why it was done, as far as I could work out it was in a time before AAV's, so have seen on long runs through lofts. On your one it may have been because they wanted to keep it open to atmosphere to speed draining or filling, is there a manifold or isolation on each drop ?

As far as I can tell, there is only the stopcock after each vent,the pipes then dissappear straight down a void in the centre of the building. there is a good fall from the tank to where they turn vertically downward. As you say it muay have just been fashionable at the time that the original tanks were installed !!!!
thanks again for your help.
Cheers

 

[dave1]

Sounds interesting I've never seen that before. Have you got/ can you get some pics of it?

 

[quattro64]

I have to go back there next week, i will try and remember to get some!

 

[stevetheplumber]

if it was me doing the job i would definatly reinstall them they were obviously put there for a reason and it will be a pain if you do it all and its a bugger to fill in theoryb they are not needed as the air should go up throught the pipework if its all falling the right way
for the sake of £20quids worth of matierials id put them back remember they will need to be grometed(sealed ) into the tank top you could even join them above the waterline to allow one pipe to be grometted