Building "Codes" Contribute to Waste
Home                                                                                                                                        Published 4/23/08

Like just about anything else the Government is involed in, certain building codes can CONTRIBUTE to waste. In this case, I'm talking about the size of the hot-water pipes in your home.

Perhaps 20 years ago, I was wiring a small Post Office that was being built. My "inquiring mind" caused me to ask the plumber about some work he was doing. A small electric water heater was located in a utility room, about 15-20 feet away from the bathrooms in the building. I asked the plumber why he was running 3/4" copper tubing for the hot water, to the sinks in the bathrooms, which seemed unneccessarily large to me. He explained that the "building codes" require a 3/4" pipe if more than one fixture will be connected to it. Later, he installed those "pushbutton" faucets on the sinks that automatically turn off after about 5 to 10 seconds. The faucets, as most do, have a "flow limiter" to reduce water usage. The limiter is simply a washer-like disc installed in the faucet's spout, with about a 1/8" hole in the middle that restricts the water flow.

My first thought was that it was silly to have to run such a large pipe to the sink, seeing that only a small amount of water would ever flow through that 1/8" hole. My second thought was that the large pipe holds a lot of water, and at that slow flow rate, it would take a long time to ever get hot water at those sinks.

After the job was complete, I tested it out, and I was right. Washing up with hot water was practically hopeless. You had to stand there for minutes, repeatedly pushing the faucet button, to finally get warm water. I don't have that kind of patience. But hey, it's "up to code".

When I later re-plumbed my parent's house, I thought of that. Seeing that I was doing the work myself, without any permits, and it would never be inspected, I decided to use my own "codes".

I located the water heater in the basement, about centered between the kitchen and the bathroom. Off the top of the water heater is about 8" of 3/4" copper pipe, including two reducing tees. From the tees, I ran a 1/2" pipe to the bathtub faucet. a 1/4" pipe to the bathroom sink, and a 1/4" pipe to the kitchen sink. I kept all the pipes as short as possible, using flexible copper tubing. Now I have nearly instant hot water at all the faucets, with minimal waste! And there is no noticeable loss of pressure or flow. (Pipe sizes shown are Inside Diameter.)

I've also seen another method of accomplishing the same thing, which involves having the hot water circulate continuously, returning back to the heater. Sometimes this can be accomplished by gravity, or in other cases by using a small pump. Besides for the energy the pump uses, a drawback to either of these methods is that it causes all of the hot-water piping to act as a radiator, continuously wasting heat, causing the water heater to run more, and in summer, the air conditioner too. Not exactly efficient!

Insulating the hot-water pipes reduces, but does not stop, heat loss from the pipes. Even with a well-insulated pipe, the water will cool off in about 15 minutes, when not in use. Besides for having to waste this cooled-off water in the pipe, the pipe itself has cooled off too. That means that the hot water coming from the heater will give up much of it's heat to simply warm the pipe up again. That's why the water gets hot gradually as you let it run. Several times the amount of water that the pipe actually holds must be run through the pipe, before the water will reach the faucet at full temperature. Smaller pipes heat up much faster. Besides for the fact that you're wasting all of this water, an equal amount of cold water enters the water heater, for which you will be paying to heat!

Approximate water capacity of various copper tube sizes. Inside Diameter of tube is listed, Outside Diameters are approximately 1/8" larger. (Type L copper, the good stuff!)

3/4" = .23 gal per 10 feet (.25 gal = 1 Qt.)

1/2" = .1 gal per 10 feet.

3/8" = .05 gal per 10 feet.

1/4" = .025 gal per 10 feet.

As you can see, each size you go down cuts the amount of water in the pipe by about 1/2.