The Long, guilt-free shower …
Having worked for 10+ years in a food manufacturing setting something I’ve learned is that waste is the enemy. Wasted time, wasted materials, wasted finished products and, of course, wasted energy. It’s strange what you think about while taking a shower before bed—especially once you’ve added kids to your life! (do I hear a kid crying? did someone just open the door?) One such shower had me looking at my feet as the hot water swirled suds past my toes. “How old is our water heater?” I may have said that out loud — I don’t sing in the shower but sometimes, er, often talk to myself — we had just moved in and recalling the inspection report. “20 years — approximately.” Hmmm, that’s a long time for a tank water heater. Those tank water heaters of that age are 50% efficient, and that’s just for the heating of the water which just goes out to the street after a single use. Not. Very. Efficient.
“What if I could design a heat exchanger that could recover some of that heat?” I asked myself. See how how my mind can wander? I could put a car radiator in the drain and a fan that would turn on and heat the house with that energy. But only in the winter of course. And the small passages of the radiator would get fouled with soap, my wife’s hair and (someday) kids bath toys. The next day I searched the Internet for heat exchanger plus shower and discovered that I wasn’t going to need to invent anything and a solution was ready to purchase. The search results showed me a company called GFX (Swing-Green—link below) and their product line was a range of lengths, diameters and coil arrangements designed to fit in the household plumbing of nearly any house.
Says here on the website that cold water flowing through coiled copper tubing is wrapped around the drain pipe where hot water flowing down transfers heat to cold water headed towards your water heater recovering over 60% of the energy you spent to make it hot. This greatly reduces how hard any water heater has to work extending the life of the heater’s heating element and reducing the need for large heaters. It also said that it will pay for itself in 2–4 years depending on how often your family showers. This thing only really works when the water being heated is both flowing and draining at the same time so clothes and dishwashers that run in cycles don’t take advantage of this. Turns out, that’s OK because showering uses the vast majority of hot water use in American homes. Oh, and it’s maintenance-free. I was sold on the concept, so it was time to make a choice.
After some quick measurements of our basement drain I settled on a 36” long parallel coil 4” diameter full copper model. It cost about $450. Check out the picture. The way this system works is this: when water falls down a vertical pipe physics dictates that it will form a thin film along the inner walls of the pipe completely covering the pipe with a fast-moving sheet of water that will keep the pipe clean and efficient forever — this is never the part of your plumbing that gets clogged, and this is why. The length of the pipe is what determines how long the hot water going out will be transferring energy to the cold water coming in from the water source. The coil configuration (parallel or single) just determines how much pressure drop the wrapped incoming water will induce on the household appliances. Parallel has less of a drag and is slightly better at pulling energy out so we went that route. The diameter isn’t really up to you and is just picked to match up with size the pipe in your house.
Installation was easy enough to do myself with basic plumbing skills, tools and about $40 worth of parts. Cut 36” of drain pipe out, slip on two couplers on to the exchanger, put it in place, shift the couplers to bridge the gap at the top and bottom and tighten. Phew, now it’s safe to flush the toilets! No joke, do NOT flush the toilet with your drain stack cut open! The next part is a little more work but if the builders of your house were smart the water heater and the drain stack aren’t far apart. Now just run the water supply to the bottom of the exchanger coil and connect. Just connect the top of the heat exchanger to the inlet of the water heater and you’re done. It wasn’t quite that simple but it did just take a couple hours. If you’re less of a gambler than me, hire a plumber. The extra $200–300 to get it installed by a pro takes out the guesswork and means the payoff comes just 2–4 years later.
I can’t figure out why these aren’t required in homes. Of all the things the government makes us do, this one makes a ton of sense. So easy, no maintenance and the energy/money savings are tremendous. Just like a turbo charged car engine, the heater required to provide your house’s hot water can be significantly smaller with one of these because the heaviest water use (showering) just got 40–60% more efficient and smaller heaters are cheaper and take up less space. Heaters that work less also last longer. In an optimized house, the drain-water heat exchanger is a no brainer. Check out the URL below and reach out to me if you have any questions … I don’t sell these things but I think everyone should have one.