Combi boiler in loft - wasting loads of cold water on tap in ground floor

[Mottie]

My mate has the same problem. Either wash up in cold water or boil a kettle!

 

[GillObrien]

We have a similar issue for the shower and we just run it into a bucket until it is st temperature, then either use it straight away on the garden or, if we don't need it, put it in a water butt in the garden for later. It balances out as we turn don't run the tap for watering the garden or other outdoor use.

But yes, it's annoying.

 

[bernardgreen]

How many bowls of water will it take to repay say 1000 quid to reposition a boiler

Add the gas costs of heating a pipeful of water ( the pipe between combi and tap ) and then that pipe cooling down when the tap is turned off and the boiler shuts down.

And since it is a combi there are the unavoidable costs incurred every time the boiler fires up in response to a hot tap being turned on. Heating the mass of the heat exchanger before any heat reaches the water flowing through that heat exchanger. When the tap is turned off the heat exchanger cools down with most of that heat going out of the flue in the post-purge.

 

[gas112]

Add the gas costs of heating a pipeful of water ( the pipe between combi and tap ) and then that pipe cooling down when the tap is turned off and the boiler shuts down.

0.0000001p
10 metres of 15mm pipe holds 1.4 litres of water im sure you will work it out to see the true cost

 

[vulcancontinental]

it is more than just one bowlful. Probably several each and every day.

Do plumbers ( AKA heating engineers ) take account of wasted water when "designing" a system. After all they will not have to pay the running costs of the system they create.


When planning the plumbing for my cottage waste of water was a concern due to very long pipe runs. Solved with two hot water cylinders, one in kitchen and one in the bath room. I was lucky in that the rooms are large and space was available.

I do, I try to dissuade combis in a loft, boilers,, OK but locating a combi as far as possible from the tap you use most is not a great idea - however the customer is always right.

I think you're missing the point however, it's not the cold water you run off before the hot arrives, water goes through a cycle to be used again, it's the moment the hot tap is turned off that's the problem, there might be 30' of hot water stationary in the pipe that you've just paid for and burned a finite resource to heat that simply cools to room temp; every time you run the hot tap.

 

[DetlefSchmitz]

I make it about £10 a year, if it were electric. So presumably about a third of that for gas?

 

[Roddy Young]

0.0000001p
10 metres of 15mm pipe holds 1.4 litres of water im sure you will work it out to see the true cost

Approx 0.071kWh which at about 10p per kWh = approx 0.7p

 

[foxhole]

Its a situation most people accept , if you have a boiler in the ground kitchen you waste hot water every time you use the hot at 1st floor level.

 

[gas112]

Approx 0.071kWh which at about 10p per kWh = approx 0.7p

what temps did you work it out at starting and finishing ?

 

[Harry Bloomfield]

And since it is a combi there are the unavoidable costs incurred every time the boiler fires up in response to a hot tap being turned on. Heating the mass of the heat exchanger before any heat reaches the water flowing through that heat exchanger. When the tap is turned off the heat exchanger cools down with most of that heat going out of the flue in the post-purge.

Which is where having an open vented system, with a hw cylinder wins everytime. Less gas wastage, less water wasted and usually the hw will appear at the tap quicker with greater flow rate.

 

[gas112]

Which is where having an open vented system, with a hw cylinder wins everytime. Less gas wastage, less water wasted and usually the hw will appear at the tap quicker with greater flow rate.

so you use every bit of water that you heat and none goes to waste by cooling down sitting there stored not being used .
Combi runs for 5 minutes whilst having a shower and not at full gas rate .
From stone cold how long would your stored water have to be on to give you a 5 minute shower ,
Same as running a bath combi running say 15 minutes before adding the cold if too hot for you . How long from stone cold to heat your cylinder

 

[Johntheo5]

what temps did you work it out at starting and finishing ?

By calculation, and assuming 85% combi efficiency, the dT = 37C, (0.071*0.85*860/1.4) so maybe 20C/57C starting/finishing?.

 

[HERTS P&D]

Easy, put the kitchen in the loft!

Andy

 

[Deleted member 281264]

Unvented cylinder with system boiler on hot water priority is the best way to do it.

 

[Roddy Young]

what temps did you work it out at starting and finishing ?

Start 10°, end 60°