Plumbing ,conversion to combination boiler advice .

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All this talk of Corgi is making me nostalgic. 😁
 
I've only recently looked at the same issue and I did the sums to try and get a handle on it. A given length of 22mm copper contains 2.36 times more water than 15mm. Those figures are based on actual bore sizes of 20mm and 13mm respectively. When you translate that in KWh of heat lost it's not a very big deal, in my case 22mm pipe would lose 0.178 Kwh more heat vs using 15mm at a cost of approx. 0.8p. The cost of wasted water was higher at 1.54p. Even so It would be a long time before the cost of installing 15mm pipe paid back.
The 20mm pipe has 1.5 times the surface area to lose heat to and the water flowing through it has 2.36 times as long to lose heat to it.
The narrower pipe has 0.7 of the larger pipe's area to lose heat to and the water will be in the pipe for 0.42 of the time.
The theory that underpins microbore - no?
 
The theory that underpins microbore - no?
Micro bore for heating, not for hot & cold feeds though. Even so, never been a fan of micro bore. Looks horrid going up into a rad valve. Chrome plated 15mm looks the dogs. 🥳
 
Micro bore for heating, not for hot & cold feeds though. Even so, never been a fan of micro bore. Looks horrid going up into a rad valve. Chrome plated 15mm looks the dogs. 🥳
Damned you! That microbore pipe going into the rad I can see as I sit at this lap-top just got three times uglier and ten times more noticeable!
 
Micro bore for heating, not for hot & cold feeds though.
The principle is the same though - reduce surface area and maximise flow speed to reduce heat loss. The difference is the time a tap runs relative to a heating system - hence, your comment that it isn't worth the gain is entirely plausible.
 
I think that’s more the old ones buddy . I’m in a catch 22 , my 21 year old Vaillant is limping along so far but if I just get a new system boiler I’m screwed if I want a roof extension :( .
The 10 year warranty on the new Worcester Bosch ones seem attractive .
My parents had a Combi installed a few weeks ago and that seems fairly faultless over the old system boiler . Only issue so far is it’s making a 25year old mixer shower drip 💧.
Do look at Viessmann. I think it's been mentioned on the forum before but they have stainless steel heat exchangers so less likely to corrode over time. They are also slightly cheaper than Worcester or Vaillant
 
Another shout out for Viessmann. 👍

(although I’m not aware they are cheaper than the mentioned alternatives.)
 
Just checked on the mains outside tap , managed 19L a min :eek: . Serious pressure !
Flow rate & pressure are different.
You can test pressure with a gauge like this
 
I can't remember off hand. I seem to remember ours was 6 bar which was too much for our water softener (would have blown seals) so we had to put in a pressure reducing valve
 
I can't remember off hand. I seem to remember ours was 6 bar which was too much for our water softener (would have blown seals) so we had to put in a pressure reducing valve
The tester in the garage was broken , new one arrived today , I’ve got 4.8 Bar on the cold mains so I doubt I’m going to have any issues either way
 

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