Boiling less to brew quicker?

[kenmc]

The weather here is sh1t at the moment, rain threatened all the time. So I was wondering if it was possible to boil less than 23 litres in order to save time, and then top it up with cold water to the 23 litre mark. Or does it affect the finished product?
Was thinking that if I boiled up 12 litres or so, would only take about 20-30 mins to bring to the boil instead of an hour, boil for 60 mins as usual, and would crash cool in half the time too, especially if I added cold water to the boiler to drop the temp as well as the chiller.
So could posibly be finished a brew in 2 hours instead of 3 or 4.
Although the little 'if it sounds too good to be true it probably is' bell is ringing in my head....
Cheers
K

[steve_flack]

Also - is the cold water sterile?

[kenmc]

Also - is the cold water sterile?

enough to drink
Not sterile, but i have used the tap water unboiled for each and every kit i made in the past. dunno if that was just luck though

[PieOPah]

When I did extract brewing, I always boiled half the volume of water required and then topped with cold tap water. This was before I knew anything about hop utilisation. Still, I enjoyed the beer and the hop contribution was fine!