Hot water options for a worn-out house + renovator
August 21, 2022 7:04 AM   Subscribe

We are trying to get a battered 1922 house back online + fully functional. We're now living in it, and it's clear that the c. 1990 hot water heater has some issues, and likely needs to be replaced. What are the best, most energy efficient options that I should be thinking about right now?

Ideally I'd like to move from the "big tank of constantly heated water" approach to something like an on-demand system if possible (this is an aspect of home repair I know zero about, unfortunately).

Some other (maybe) salient details:

* It needs to serve two bathrooms + 4 people.

* Beyond replacing the fuse box w/a circuit breaker, no substantive electrical work appears to have been done on the house since it was built.

Right now, it's only producing lukewarm water, and some exterior rusting has me worrying about it failing (though the basement is unfinished w/nothing to damage in it).

I'm pretty worn out from working on this place + well past my comfort zone w/its various plumbing issues, so hopeful the hivemind can point me in the right direction. I'd like to be speaking from a position of slightly less ignorance before I call in a plumber.
posted by ryanshepard to Home & Garden (18 answers total) 1 user marked this as a favorite
Recommend a tankless water heater, we have this one. Hot water is on demand and you don't need to worry about the bottom rusting out. Depending on where you are, you can get it installed outside the house which is helpful for exhaust. Keep in mind that like with any water heater (tankless or not), where you install it will effect how long it takes to get hot water into your faucet.
posted by Toddles at 7:18 AM on August 21, 2022 [1 favorite]

Best answer: Is the current water heater electric or gas?

The upside of replacing with another water heater is that it's a relatively easy and inexpensive job. If it's electric, you probably don't want to replace with another electric heater that draws more current unless you get an electrician to determine it's OK. It could be a rapidly ballooning job upgrading the associated electrical.

Several years back, I replaced the water heater in my 1930s house with a tankless system. Talk about rapidly ballooning job! In the end, I could have replaced the old gas water heater several times over for the the rest of my life for a fraction of what I ended up paying for the tankless system. Mostly because the original gas line was really too small to service the tankless sytem, which needs a large volume of gas to heat water on demand. Strike one. Our tankless sytem also needs a trivial amount of electricity to run. We don't have power outages often, but they do happen occasionally, during which, we don't have hot water. Strike two. I've found it takes a few seconds for the tankless system to sense when hot water is needed, and appropriately allow it to flow. As a result, when I'd occasionally turn off the shower tap to save water while showering, turning back on means getting blasted with a couple seconds worth of cold water before the hot mixes back in. Strike three.

The savings of gas seems to have been small enough that we never noticed any difference in the actual gas bill. So, yeah, I have pretty mixed feelings about going tankless. The biggest upside for us was that the water heater was relocated outside the house, freeing up a bit of space. I'm not saying tankless will be a bad idea. I am saying it's been, in retrospect, not a clear winner for our needs. The issues I've encountered may not be issues at all for you.
posted by 2N2222 at 7:33 AM on August 21, 2022 [3 favorites]

We have a similarly old house, and we have a gas tankless heater that we absolutely love. That said, I do agree with 2N2222 that it's likely to be a fairly significant project either way. My experience with electric tankless water heaters has not been great, but there may be better ones on the market than the last one I had. But I would not trust non-updated wiring with that kind of a load. And the gas demands for a gas tankless water heater are significant, so if you don't already have a sufficient supply line in place, that's going to cost some money.

I still think it's worth it, primarily for the unlimited supply of very hot water — no need to worry about multiple people taking showers in a row, taking a shower at the same time that the laundry is running (except maybe for water pressure reasons), etc. Does it save money? Honestly, I have no idea. Our gas bill is very small, and I don't know what it would be with a traditional water heater. That's not really a factor in our satisfaction. We just enjoy how well it works.
posted by primethyme at 7:44 AM on August 21, 2022

Response by poster: Is the current water heater electric or gas?

posted by ryanshepard at 7:52 AM on August 21, 2022

Several years back, I replaced the water heater in my 1930s house with a tankless system. Talk about rapidly ballooning job! In the end, I could have replaced the old gas water heater several times over for the the rest of my life for a fraction of what I ended up paying for the tankless system.

I put in a tankless system some years back in a previous house. There's no way it made financial sense (between minor electrical work, running a gas line extension, etc) but it saved a large amount of space in a small house so was worth it that way alone. We did end up needing to put in a recirculating pump to deal with the long delays for getting hot water to faucets -- depending on the layout of your house, this may be essential or optional.

Lowest cost and hassle is definitely going to a replacement in kind with whatever you have there now.
posted by Dip Flash at 8:14 AM on August 21, 2022

If your current heating system is a boiler and you are in a cold climate, an indirect hot water heater may be a good choice: it has a storage tank but uses the boiler to heat it. A lot does depend on your specific situation though.

Here is a general guide to your options:
posted by metasarah at 8:29 AM on August 21, 2022 [1 favorite]

Electric heat pump hot water heaters are the current favorite for high efficiency. Our power company in Austin is giving rebates on them.

They are a little larger than other tank water heaters, and need a little bit of space for ventilation.
posted by bug138 at 8:30 AM on August 21, 2022 [2 favorites]

Best answer: Metafilter seems to lean against tankless heaters but we like ours. For whatever reasons of piping and water pressure we have never found ours to be significantly slower to get hot water to a given tap than the old tank had been. Hot water is indeed slow to arrive at the kitchen sink, but it was slow before; the master bathroom in our DC rowhouse is two floors up, but it’s a straight pipe run from the heater and the hot water there is almost imperceptibly slower than it was before. Our gas bill didn’t really change with the switch. We needed a higher capacity gas line run to the utility closet, but I don’t think they charged us for the work. Our house is on an alley and the utility closet is on an exterior wall, so they met venting requirements by cutting a hole and running the exhaust straight out. If your heater can’t go near an outside wall, it might not be possible to install a tankless heater at all, since the venting requirements are very specific.

At this point my biggest concern with a tankless gas heater like ours is the fact it burns a fossil fuel and contributes however much pollution. I love the fact we can have my whole family visit and never run out of hot water as people take showers, but I might not replace it with another gas heater for environmental reasons.
posted by fedward at 8:42 AM on August 21, 2022 [1 favorite]

Best answer: If I were doing a whole house renovation I’d look pretty seriously at the European approach of a smaller on demand heater at each point of use instead of a central tank. Then you never have the problem of the one room at the farthest end of the house that takes forever to get hot water, like my parents’ master bathroom. It’s probably a bigger job than you’re up for right now, though.
posted by fedward at 8:51 AM on August 21, 2022 [2 favorites]

Best answer: From anecdotal evidence, the other problem with gas-fired tankless systems is the exhaust. In your old gas heater the exhaust was warm and carried up the flue on its own buoyancy. In tankless systems the exhaust is forced out with a fan. If your flue is shared with your home furnace/HVAC system those fumes will be pushed back down into the basement.

So that means you need to add a second flue system. There are newer high-efficiency water heaters that vent out a cold PVC pipe and if you can swing one of those, that would be easier to install than having your sheet metal reworked.

And, to add on to 2N2222's problems, if you have a high-efficiency washer you will have the same trouble as the shower. The washers draw such little hot water that the tankless system never fully kicks in. You'd need to run a nearby tap for a while to get things up to temperature.
posted by JoeZydeco at 9:13 AM on August 21, 2022

Best answer: If you can wait a little while for states to set up their programs from the Inflation Reduction Act funding, you may be able to get a rebate on an efficient heater. I think a heat pump water heater also qualifies for a separate tax credit. Definitely choose a fossil-free option!
posted by pinochiette at 9:59 AM on August 21, 2022 [2 favorites]

Best answer: The just-passed climate bill has a PILE of incentives in it for electrification, which in this case means a heat pump hot water heater. If at all possible I would take a breather to see how the incentive structure is going to shake out.
posted by rockindata at 9:59 AM on August 21, 2022

Best answer: Oh yeah, before you buy anything make sure you check the DC Sustainable Energy Utility web site for applicable local rebates. We got money from them when we installed our on-demand water heater and an eligible high efficiency furnace and AC combo. When we did it nine years ago it was still a pretty new program and we had to prod the HVAC contractors to provide the right paperwork in the right way to prove our eligibility, but I'd hope most of the big contractors now are used to compliance by now.
posted by fedward at 10:19 AM on August 21, 2022

Best answer: We just replaced a gas on demand unit, which was working fine, with an electric heat pump unit. Would definitely not recommend the gas on demand option. It is slow to get hot water and it is not efficient to have the unit fire up for a few seconds (and then run the fan for five minutes) whenever a little bit of hot water was needed. We found it did not work well with the front loading washing machine, which sprayed warm water into the tub over about 10 minutes, resulting in the heater turning on and off for that entire period, but never really putting much hot water into use. It took a long time to get hot water for a shower and was completely unusable for a little hot water for hand washing. It wasn't just a long wait, but it also made the warm water in the pipes unusable for showering because there was a slight delay for the unit to turn on resulting in warm water followed by a bit of very cold water and then hot water, so you could get in the shower until the cold water section had passed.

Point of use electric on demand works for some, but isn't generally practical in retrofits because of the large amount of power required for each unit and it isn't very efficient. Central on demand gas is a dumb idea and I can't recommend more strongly against it. The heat pump electric tank is great and very efficient. I'm sure the standby losses are more than offset by the heat pump efficiency, so less electricity is required overall than point of use electric.

If you tank is only producing warm water now, it is likely that the problem is one or both of the heating elements are weak or dead. You can test them with a multimeter and replace as needed for not too much money to keep it running until you can make the move to a heat pump unit, if waiting for potential incentives makes sense for you.
posted by ssg at 11:16 AM on August 21, 2022 [2 favorites]

It's possible that there's nothing wrong with your current water heater. Many of the 'big tank of hot water' systems actually use a heat exchange model where the element heats a tank of water that the actual hot water lines run through and take heat from the tank to heat the water running through the line. The level of the tank full of water will drop over time, especially if the thermostat is not working correctly and overheating the tank. This results in less water in the tank and resulting lower heating of the water running through the pipe. There should be a valve that looks like a bent lever and a drain pipe coming out of it. You can open this valve and should hear or see water (hot) coming out of the drain. if water doesn't come out, keep holding the valve open until water comes out. This will ensure the tank is full.

if that doesn't work or you just want to change to a more efficient heater, there are lots of options. Most new systems are a 'heat pump' style that is much more efficient than the older ones, but still use a tank. if you live somewhere with enough sun, solar is the best way to go and these can have the tank in the normal place fed by a remote solar panel or one with the tank and panel together on the roof (saves space inside the house, but make sure your roof is strong enough for the weight of the tank).

If you already have gas, an on-demand system can be great - you only pay to heat the water you use and you have unlimited hot water when you need it. I installed these in a house I built and they were fantastic - you can get 'smart' systems that allow you to limit the amount of hot water used in one go if you (eg) have kids that want to take ridiculously long showers.

Note that the time taken to get hot water to all the taps is purely a result of the distance between the hot water source and the tap, not the type of heater. In the house I built, the bathrooms were a long way apart, so we installed two heaters. We installed them outside so had no issues with getting rid of heat.

My preference would be solar first, then tankless, then heat pump. When our current tank/electric system dies, it will be getting replaced with a solar system on the roof so we can reclaim the space used by our inside tank system (if we had gas it would be a tankless system).
posted by dg at 2:45 PM on August 21, 2022

Go with electric for environmental reasons and lower utility bills.
posted by slidell at 3:01 PM on August 21, 2022

Note that the time taken to get hot water to all the taps is purely a result of the distance between the hot water source and the tap, not the type of heater.

With a tankless heater, first the water starts flowing (e.g., you open the faucet), then the heater kicks on, then it starts heating water, then the now-hot water starts heading to the faucet. So there's an extra delay built in that, in addition to a longer wait for hot water, can be an issue for all the things explained above -- efficient appliances, people who want to shut the shower off for a moment, and so on.

This is why frequently people install recirculating pumps with a tankless heater, to keep hot water circulating at the times of day when they know hot water will be needed.
posted by Dip Flash at 3:22 PM on August 21, 2022

You have already gotten a lot of great advice in this thread. I too would suggest waiting and taking advantage of one of the new government incentives. I have a electric heat pump water heater that works great.

But I would also mention that there are electric tankless water heaters.
posted by bove at 12:40 PM on August 24, 2022

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