What size hot water pipes

[bradhawkins7]

I am replacing the galvanised pipe supplying my hot water with new copper pipe. The galvanised pipes naturally look bigger that their copper equivalents but looking at the bore (I cut the pipes) I would say that the pipe is currently equivalent to a 22mm to the bottom of the riser and from there on a 15mm.

I was keen to use 22mm pipe as far as possible to keep the headloss to a minimum, but read on one of the blogs that this is not always a good idea with hot water as you have to wait for all the cold water to empty out of the tap before you get to the hot water.
Please could you look at my sketch with proposed pipe sizes and pipe lengths and let me know if this is ok. Bear in mid that at present the pressure is fine.

Thanks

Untitled

• bradhawkins7
• 23 Jun 2009
• 1

 

[charliechaplinspants]

If it`s gravity, ( hot water from a cylinder, tanks in loft ) you are best dropping the hot in 22mm.

 

[bradhawkins7]

Ok - so I will put in a 22mm from the cylinder to the mixer. The branches to the basin and to the kitchen - should they be 15mm?

 

[charliechaplinspants]

To basin ok in 15mm, why are you going from the bath back up to the kitchen?

 

[bradhawkins7]

The kitchen has a hot water outlet. At present there is a galvanised pipe from the bathroom to the kitchen. I want to change it to copper.

 

[charliechaplinspants]

Something does not look right, are you sure other pipe is hot water pipe? it seems pointless to have two hot water feeds dropping into bathroom. could you not cap this pipe under bath, find out where it`s coming from and take hot feed to kitchen from next floor up? that would make more sense, puzzled as to why it would drop down in 22mm and 15mm.

 

[bradhawkins7]

The larger galvanised pipe enters the bathroom and goes to the bath mixer. It then reduces to a 15mm equivalent galvanised pipe which is continued. From this continuation, there is a branch which goes to the basin in the bathroom and the 15mm galvanised equivalent continues to the kitchen.

 

[charliechaplinspants]

I know, but I would have expected one drop into the bathroom to feed bath/basin and kitchen to be fed from the floor it is already on, there is no point in dropping down to bathroom then going back up to where it has already came from, it makes no sense especially since it`s gravity fed, is there any reason why the hot water to the kitchen could not be supplied from the floor it is already on?

 

[bradhawkins7]

The hot water cylinder is on 1st floor. The bathroom and kitchen are on ground floor.

 

[charliechaplinspants]

your sketch suggests the hot water pipe runs back up to upper floor, keep bath feed in 22mm all else, ok in 15mm

 

[bradhawkins7]

Thank you