Re: plumbing : it takes ages to get hot water in sink
While a clogged pipe can certainly slow down the flow and make water take longer, a pipe that's too large can also be a problem. Sometimes people install pipes that are too big, thinking that the water will flow faster, but that's not necessarily the case.
Think about this: there is a flow restrictor in the typical faucet aerator that has a hole not much bigger than a pencil lead, limiting it to 1.5 gallons per minute. Whether the pipe is 1/2" or 3/4" isn't going to make any difference in the speed that water comes out of the faucet. Even though a 3/4" pipe has a flow capacity of around 23 GPM* and a 1/2" pipe is around 14 GPM, you're still limited by the faucet at 1.5 GPM. However, a 3/4" pipe has about twice the static capacity of a 1/2" pipe. This means for, say, 10 feet of pipe, it will take twice as long to empty the cold water out of a 3/4" pipe as it does out of a 1/2" pipe!
Despite all this, it is necessary to use larger pipes to supply higher demands. I haven't been in the plumbing industry for 14 years and codes may have changed, but back then you had to size your pipes assuming every fixture was in use simultaneously. This meant that from the water heater to a master bathroom with double sinks, two showerheads, a soaking tub, and a toilet (it was a fancy house) we had to run 3/4" pipe, despite the fact that in normal use you'd NEVER have more than two fixtures running at a time (therefore never needing the capacity of a 3/4" pipe). This is an example of a code that drives inefficiency: because of the greater volume of "hot" water that sits in the pipe cooling off, more water is wasted waiting for the hot water, and more energy is wasted through heat loss. Couple that with the fact that a McMansion might have the master bath a long ways from the water heater, and the problem is even worse.
* The flow rates mentioned were determined by 15 seconds of Google searching.
Last edited by Fencepost; 02-04-2013 at 12:43 AM.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.