32mm overflow on cold water tank?

[Anna Rack]

We're selling our house, and the surveyor advised that the current 21.5mm overflow from the loft cold water and central heating expansion tank is too small, and needs to be 32mm!
This seems huge to me, and will present a problem when exiting under the eaves. I'm going to change it to keep our buyers happy, but my local plumbing centre says no-one uses anything this big for an overflow. It does run horizontal for a couple of metres, though.
Does this seem reasonable? Any recommendations for an online supplier for the pipe and fittings?
Thanks for any advice.

 

[gasmanrob]

only reasons i could think of for needing something of that size would be both your overflows run into one pipe in which case it may be easier to just run to seperate overflows.

Or your water tank is the size of a transit van and your in coming water supply has more power then a fire engine pump!

If its really that mush of an issue come out of the tank in 21.5 with a bylaw kit then use reducers to get you to 32mm then run the rest as you need.
oh and good luck trying to get 32mm out through the eaves/sofits.

come to thing of it using 32mm like that would provide a nice entrance or nest for anything that can get in it and would leave you worse of then just keeping the 21.5

any more details on why he has suggested the upgrade would help in directing you down the best route

 

[johnnyplumb]

We're selling our house, and the surveyor advised that the current 21.5mm overflow from the loft cold water and central heating expansion tank is too small, and needs to be 32mm!
This seems huge to me, and will present a problem when exiting under the eaves. I'm going to change it to keep our buyers happy, but my local plumbing centre says no-one uses anything this big for an overflow. It does run horizontal for a couple of metres, though.
Does this seem reasonable? Any recommendations for an online supplier for the pipe and fittings?
Thanks for any advice.

which part of the country are you in ?
the byelaws used to be different in scotland than england, dont know if it's still the same.

up here in scotland, for say a standard 50g tank with 22mm inlet pipe, the overflow pipe would be 40mm to the outside and 32mm for the f&e tank.

the regs say that the overflow pipe needs to be twice the diameter of the inlet pipe or 2 1/2 times if a filtered overflow [ in scotland ]

 

[Simon F]

Hello Anna and :welcome:
what size is the cold feed to the tank, if its 15mm then 21.5mm overflow is standard size
if the feed is 22mm then you need to go bigger on the overflow

 

[Anna Rack]

Thanks for the replies. I'm in Kent.

The cold water tank and central heating tank are next to each other, and both feed into a tee which exits via the one 21.5mm overflow pipe.

Both tanks are fed by 15mm cold feed.

I can't really contest the surveyor's findings as the overflow pipe and a dripping ball valve are all he found on a 30 year old house! He said that becuase of the mains pressure being potentially very high the overflow wouldn't cope!

 

[petercj]

Could you perhaps run another 21.5 alongside the existing pipe ... 2 x 21.5 = 43

 

[Guest123]

Should be 11/2 pipe as Johnnyplumb says above.

 

[stevetheplumber]

Should be 11/2 pipe as Johnnyplumb says above.

only in that cold dingy bit of the uk thats north of the wall 2 x 21.5 is fine in the sunny south

 

[Guest123]

only in that cold dingy bit of the uk thats north of the wall 2 x 21.5 is fine in the sunny south

Our regs are perfect, you lot using tiny wee overflow pipes are bloody miserable saving your cash instead of doing it the correct way as we North of the Border geniuses do in all our work.

 

[johnnyplumb]

only in that cold dingy bit of the uk thats north of the wall 2 x 21.5 is fine in the sunny south

aye, but you'll know be saying that when the waters running into the tank quicker than it can run out the overflow :cheesy:


the hot & sunny weather you get down there though, might just help to dry out the ceilingsand carpets afterwards :cheesy:

 

[Mike Jackson]

Having the overflows teed together is a breach of the water regulations regardless of the size.

 

[petercj]

Having the overflows teed together is a breach of the water regulations regardless of the size.

So wouldn't it make sense to run two 21.5 pipes - one from each tank?

 

[AWheating]

the 21.5mm pipe is a warning pipe rather than an overflow pipe. Its main use is to warn there is a problem not stop the tank overflowing which is why is should be positioned as to cause a nuisance/be visable. sounds like the best solution is to install another 21.5mm pipe so each tank has its own and you wont have to try and get a large dia pipe to outside.

 

[Best]

They have been using 21.5mm pipe here for last few years & I also doubt it will cope in a real bad overflow. It is not so bad if the 21.5mm o/f has the proper byelaw tank fitting turning down into water in tank & that the pipe terminates much lower than the tank, as it will draw the water away better.
Far better with bigger pipe IMO, but then toilets have small o/f pipes, although the mains fed toilets really should have restricted fill valves fitted.

 

[Anna Rack]

Interesting answers - thanks.
Where the pipe exits under the eaves (tile clad wall) there's a cutout in the top tile which may just be big enough to squeeze the bigger pipe through - if I were to fit 2 x 21.5mm pipes it would involve removing and cutting the tile - not easy as there's a conservatory underneath!
If you're not allowed a Tee that means fitting 2 x 32mm pipes, madness!