Getting In Hot Water
As homes become more and more efficient, we need to look for new frontiers in energy and resource conservation. One of the next ones on the horizon is water heating. We have many great options for heating water efficiently including tankless heaters, super high efficiency tank units, geothermal, and solar. They all have their pros and cons, depending on the particular project. One thing that they all have in common is that none of them are effective when connected to a poorly designed hot water distribution system.
It’s the piping, stupid!
I have heard stories of homeowners replacing their old tank water heater with a new tankless unit, only to be upset that the hot water didn’t arrive at their faucet instantly, and incorrectly blaming it on the new heater. The tankless heater was working perfectly, heating water only when needed, but the problem arises when that nice hot water needs to travel seventy or eighty feet to the fixtures, wasting water which runs down the drain waiting for the hot water to arrive, and wasting any energy used to heat water that remains in the pipes and cools off. We need to reconsider how we move hot water around the house using structured plumbing systems, on demand hot water pumps, and just plain common sense when designing our homes.
Bad Design is Hard to Overcome
We put too little thought into our house design, sticking bathrooms all over the place, with the master usually about 100 feet from the water heater. Those distant bathrooms cause us to waste water as it runs down the drain waiting for hot water to arrive at the fixtures. Low flow fixtures make this even more annoying – 1.5 gallons per minute is slower than 2.5 gallons per minute – DUH! Let’s start by putting the bathrooms close to the heaters and to each other. We save pipe, time, and water. When that isn’t possible, place the fixtures in as many groups as possible. Then design your hot water pipe system to get the water there as fast as possible. Straight runs, limited elbows to slow the flow, and pipe insulation. Check out on-demand pumps that move the hot water to the fixtures only when you need it, recirculating cold water back to the heater. Check out this demand system design in our strategies section.
How much water is enough?
Americans use about 150 gallons of water per day, including personal use as well as their share of commercial, industrial, and power generation needs. This compares to 31 gallons in the UK, and 5 gallons in Africa. We don’t need to lower our water use by 95% overnight, but it sure seems like we could cut down pretty dramatically without any major sacrifices in our lifestyles. Simple things like high efficiency fixtures are easy fixes. Maybe we could cut out a few heads in those spa showers — say, not put more than two in a stall (OK, three if you behave). Don’t run the water when you shave or wash dishes, and, finally, fix those damn leaks.
Feb 14, 2009 8:49 AM ET
Feb 14, 2009 12:49 PM ET