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Ideas From Ed: Really in Hot Water Now

Updated: Nov 8, 2020

Ed is a do-it-yourselfer who is happy to share some of his ideas and experiences in this monthly column.

This is another one of my sagas that’s not really a “restoration” project, but showcases one way to fix an ongoing issue and go a bit high-tech. The problem is that sooner or later, every hot water tank will need replacing. It might have a crusty anode rod and doesn’t work like it should, or the bottom is rusting and leaking, or need some replacement control that’s made of “unobtainium” because of its age. A typical tank isn’t real efficient because it heats water even if you’re not using it. Forty, fifty, or more gallons of water take up a lot of space, too.

Current code requirements in most places make you install a pan under the tank to “catch” leaks, a check valve in the main line, and a compression bladder/tank. Those last two items are so that as water expands and contracts as it heats and cools, it won’t force YOUR water back into the main water line. An alternative that is an easy installation, takes up WAY less space, and is super efficient, is to install an on-demand water heater. Those only heat water as it’s being used, and are available in natural gas, propane, and electric models. In the installation we’ll be discussing here, I’m replacing a natural-gas-fired heater with an electric model. No high pressure overflow valve is needed, no pan, no compression bladder, and no check valve. Here’s a picture of the old tank:

If you’re considering doing what I did, you need to know a couple of important things relative to your water usage and the available electric power. These units are sized for their flow capacity. A small unit might service a single location like a bathroom, but will be overtaxed if you are running a dishwasher, taking a shower, and washing clothes at the same time. You will need to determine the amount of hot water you will be demanding and compare the “gallons per minute” of your requirement to the unit’s output. These units use a LOT of power to “instantly” heat the water so you will also need to have an appropriate breaker panel and service line. The small unit I just installed was rated for one to one-and-a-half “users”, like a shower and a sink, and you need to have a minimum of 150 amp service. It took two 40A 240V breakers in tandem, wired through #8 wire, to supply the power. The next larger unit needed #6 wire, a 200 amp service, and 2 50A breakers! Cranking one of these puppies up will make your lights go slightly dim because of the current draw!

Here’s the old tank removed. Note the shutoff valve on the cold supply side. Prior to this picture, of course, the water heater was turned off, the supply valve closed, an upstairs hot faucet opened, a hose hooked up to the tank drain, and all the water discharged, before moving the tank. The plugged pipe on the left side coming down from the top is the old gas supply line. That feed to the tank was also uncoupled, Teflon pipe “dope” smeared around the plug threads, and the gas supply line blocked. I’ve said in other “Ideas” columns that I like the Teflon paste more than Teflon tape for certain things (like gas lines), and you should use black iron, not galvanized, fittings.

Also note that the vent into the chimney has been plugged with fiberglas insulation – the chimney no longer has a purpose as the furnace is also a high-efficiency model venting directly outdoors through a PVC pipe. In fact, installing a vent-free water heater in this situation solves the “orphaned water heater” effect. In houses with older furnaces using chimneys, some of the furnace heat helps to keep the chimney warm in the winter. That means that water heater venting is more efficient, as warm air rises. Once a high efficiency furnace is installed and furnace heat no longer helps keep the chimney warm, sometimes a water heater cannot vent properly. This might cause dangerous fumes to remain in the house.

Here you can see the “guts” of the unit, after attaching it to the wall. This thing is SMALL and LIGHT, and I used three ¼” Tapcon screws to anchor it to the brick. The water inlets are on the bottom, as are the knock-outs where the electric supply wires will enter.

Speaking of electric supply, here’s the breaker panel I was working with. There were lots of available spaces to insert the breakers. I used the bottom right 4 slots, keeping everything together. Note that I will not be trying to explain the wiring any more than I’ve already done. If you understand and are comfortable working with electricity, this is an easy job. If you’re not, HIRE AN ELECTRICIAN. Don’t risk killing yourself or think you are an expert after reading 10 paragraphs of “how-to” or watching a video clip online!

OK. So with power lines run but kept off until the unit is full of water, here’s what it looked like. The cold water inlet must be removable so that the inner screen can be cleaned once in a while.

I had all sorts of copper fittings on hand, plus a propane torch, solder, etc., in case I had to modify the existing runs of copper pipe to enable the hookups. However, I also brought two 18” water heater connecting “hoses”, one with a shutoff valve, and both with slip-fit “Sharkbite” connectors. I was able to cut the existing pipes with a tubing cutter in just the right spot to enable the super-easy connections using those hoses. I ran a final check of everything, then powered-up the two circuit breakers. Finally, it was just a matter of setting the desired water temperature with the digital display and dial. One drawback, though: Since the hot supply lines in your house won’t already be filled with warm water from your tank heater, it will take longer to get heated water to the fixture. All of the standing water (at house temperature) in the lines between the on-demand heater and your open fixture will need to run out before the “new” hot water reaches that point. SO, you will use a bit more water, running the hot side until it actually gets hot. Once it does, however, the pre-set temperature should be maintained. Obviously, this issue becomes greater when the location of the new heater is further from the point where you will be using the hot water. In new construction, it’s possible to install a recirculating pump to evacuate the lines without wasting water, but this is very difficult to add into an existing system.

Ready to shower!

I hope all your projects go well. Thanks for reading, and happy restoring!


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