15mm pipe turns into 22mm pipe. Why?

[dance621]

In my 1950s bungalow I have a combi boiler. The pipes going from boiler to the main part of the house are 15mm. I recently lifted the floor and noticed they turn into 22mm pipe in sections before turning back into 15mm for the rads.

I am thinking about swapping out the 22mm middle section so the whole system is 15mm. Is there any issue with doing this? Does a 22mm section in the middle of a 15mm run make any sense?

Thinking about using buteline by the way

Thanks

 

[kidgreen61]

Your existing 22mm copper will be a leftover of a gravity fed system, by all means change it to 15mm.

 

[oldbutnotdead]

Just to be clear, is this on the hot water side of the combi or the heating flow and return? (Would be unusual for F & R to be 15mm from the boiler, though possible in a small install)

 

[Wayners]

Mine was 15mm cold and 22mm hot because 22mm was used on gravity system from tank.
When combi boiler was fitted the 22mm was swapped to 15mm but I can't see it makes any difference to flow. I was told it does

 

[Madrab]

.

 

[fixitflav]

Does a 22mm section in the middle of a 15mm run make any sense?

Not particularly, but I can't see how it does any harm. Is there some reason you're thinking of changing it?

 

[oilhead]

If it ain't broke, don't fix it.

 

[dance621]

Not particularly, but I can't see how it does any harm. Is there some reason you're thinking of changing it?

There is lots of 10mm bendy pipes coming off the 15mm pipe. I just thought easier to rip it all out and replace it all.

 

[Madrab]

Just re-read the OP. Just leave it alone. If everything heats up ok then no need to alter.

 

[fixitflav]

There is lots of 10mm bendy pipes coming off the 15mm pipe. I just thought easier to rip it all out and replace it all.

But you haven't told us why you're thinking of doing it. Is there a problem with the existing set-up? Are you thinking of changing the rads? If so, why? I second Madrab!

 

[Madrab]

Don't get me wrong, I'm a firm believer in a 22mm backbone and 15mm to all the rads for CH, quick heat up times, easier balancing and faster to clean if and when required but wouldn't just do it for the sake of it.

If the system is ever to be upgraded, changed, renewed etc, that would be the time to do it IMO

 

[dance621]

But you haven't told us why you're thinking of doing it. Is there a problem with the existing set-up? Are you thinking of changing the rads? If so, why? I second Madrab!

Yes plenty of reasons to replace unfortunately. Much of the copper 15mm pipe went a foot up a wall that has been removed so is now suspended in mid air. Also the bendy 10mm pipe to the rads is badly twisted in places and maybe can npot be reconnected to the new rads. So the start and end of the run needs replacing. So rather than connect the new sections back to the middle 4ft of 22mm pipe I thought just keep it all 15mm.

 

[fixitflav]

Yes plenty of reasons to replace unfortunately. Much of the copper 15mm pipe went a foot up a wall that has been removed so is now suspended in mid air. Also the bendy 10mm pipe to the rads is badly twisted in places and maybe can npot be reconnected to the new rads. So the start and end of the run needs replacing. So rather than connect the new sections back to the middle 4ft of 22mm pipe I thought just keep it all 15mm.

OK, but where does the 10mm bendy pipe come in? Original post says 15mm (and 22mm)