Using micro-bore to speed up the arrival of hot water at a basin: sensible or not?

[Mark Ribbands]

I’ve recently refitted my downstairs shower room.

The hot water arrives at the shower via existing 22mm copper from the new pressurised hot water cylinder.

There’s also a wash basin teed off from the 22mm copper. Note that the shower is not much used in this room - it’s primarily a guest WC.

The hot water takes ages to arrive at the quite low-flow wash basin tap (a funky Vado electric contraption).

It’s OK when showering – the percentage loss in the pipes compared with the total consumption is probably negligible. But there must be a lot of wasted heat in filling and heating all that 22mm copper, just to rinse your hands.

I’m thinking of running a well-insulated parallel 10mm plastic pipe, teed-off from the 22mm near to the hot water tank, to supply only the wash basin. (Plus of course a restricted mains cold supply to balance the H&C pressures at the basin.)

Since the pipe volume of about 15m of 10mm is much less than 22mm, and it’s ‘warm’ plastic, I assume this would make the hot water arrive much faster when using only the basin tap.

This seems like common sense, and if so is it standard practice? Or maybe I’ve not thought of something?

I am not a plumber, so any advice is appreciated!

Cheers, Mark

 

[Nat]

Re: Using micro-bore to speed up the arrival of hot water at a basin: sensible or not

Have you thought about installing a hot return instead? That would sort your problem out. Does the unvented cylinder have a tapping for a hot return?

 

[bob the plumber]

Re: Using micro-bore to speed up the arrival of hot water at a basin: sensible or not

i cant see there being a problem, it will reduce your draw off before heat comes through. My mums house runs off a similar system to yours, mains pressure but through a thermal store, 22mm hot broken off into seperate 10mm feeds to all basins so that it more efficient

 

[SimonJohns]

I would run the secondary return pump.

If your going to run the 10mm. It's no different

 

[Mark Ribbands]

Re: Using micro-bore to speed up the arrival of hot water at a basin: sensible or not

Many thanks for the helpful replies!

Nat, Simon: Yes there is a ¾” tapping for a hot return – I didn’t understand what it was for so blanked it off.

If the hot water runs out to the taps then back to a return tapping, does it need a pump to keep it circulating? Or does the natural temperature differential cause slow movement round the loop even when all the taps are off?

It that how it’s done in hotels where many taps all produce instant hot water? Presumably an insulated pipe loop is effectively an extension of the hot water storage vessel.

But isn’t that wasteful due to heat leakage if the water is not used for a long time? No insulation is perfect.

Bob: Do the 10mm supplies work? Does the hot water arrive in a reasonable time?

Cheers, Mark

 

[Nat]

Re: Using micro-bore to speed up the arrival of hot water at a basin: sensible or not

Yes you would need to install a pump with this type of system (bronze) that can run constantly or on a timer. Obviously the pump requires electricity to run so you would be using energy there. If the circuit is laglagged well enough then you should keep lost heat down to a minimum.

I don't think I can fault your logic on running 10mm though. It should shorten the wait for hot water but by how much I couldn't tell you. I guess you could work it out if you had the time and the inclination. I wouldn't expect a great flow rate through 10mm but I guess you don't need it for a basin.

 

[bob the plumber]

Re: Using micro-bore to speed up the arrival of hot water at a basin: sensible or not

Many thanks for the helpful replies!

Nat, Simon: Yes there is a ¾” tapping for a hot return – I didn’t understand what it was for so blanked it off.

If the hot water runs out to the taps then back to a return tapping, does it need a pump to keep it circulating? Or does the natural temperature differential cause slow movement round the loop even when all the taps are off?

It that how it’s done in hotels where many taps all produce instant hot water? Presumably an insulated pipe loop is effectively an extension of the hot water storage vessel.

But isn’t that wasteful due to heat leakage if the water is not used for a long time? No insulation is perfect.

Bob: Do the 10mm supplies work? Does the hot water arrive in a reasonable time?

Cheers, Mark

the hot water arrives very quickly with good flow, my mums basin hot produces over 15 litres pm which is more than enough all through 10mm, all this talk of a secondary return is a waste of time if you ask me, bronze pump required and obviously putting in a return hot from near the tap, waste of money and a lot of messing especially if all you want is more efficiency