First Report on the Tankless Water Heater

We’ve been using our Rheem RTG-53PVP for about eight weeks now, long enough to form an initial impression. Here’s what we’ve discovered so far. Basically, the news is good.


If you are like we are and have always used a conventional water heater with a holding tank, the first thing you will like about going tankless is how much space you pick up. We had admittedly oversized the tank of the water heater in our suburban home, but even if you’re using the conventional 40 gallon tank, your water heater is taking up a minimum of four square feet of your home, and substituting a tankless heater for it will provide some extra space. Our unit fits on the wall of the shop adjacent to the apartment, taking up about the same amount of space as an electrical circuit box.

Because our water heater is mounted on an interior wall, it must be vented to the outside. Our vent goes straight up and through the metal roof. We know the gases in the vent pipe are not very hot, because we operated the heater unvented for a couple of weeks in the wide open shop. At the invitation of Tim Ledbetter, our plumber, we held our hand directly over the water heater as it operated. There was hot air coming out, but not nearly hot enough to burn you. You could hold your hand over the exhaust about as long as you wanted without pain. Tim says, and we believe him, that the gases are cool coming out of the heater because it’s using the heat so efficiently.

My guess is that the main function of the venting is to deal not with the heat but with the moisture. Any gas appliance is going to offload a great deal of moisture in its exhaust, and our water heater is no exception. When we were holding our hand over the exhaust, we felt the moisture on our skin.

It’s too soon for us to tell you how much propane we’re using. We do have the advantage of using the propane only for the water heater and the standby generator, so unless we have a power failure we should be able to monitor gas usage for the water heater easily just by seeing how often we have to refill the tank.

There is one issue with our model that was initially frustrating to us, so I’ll tell you about it. If you ask for a trickle of hot water, the water heater will never turn on. The “minimum flow,” the lowest amount of hot water the unit will produce, is .66 gallons per minute. That’s a pretty good flow of water you must call for just to get the heater running. Initially, it caused a problem in our indoor shower, namely that the woman I love took a cold shower because the shower valve even at full hot water was not calling for more than .66 gallons per minute. When Mama takes a cold shower, everyone springs into action, including Tim. He tinkered with the shower valve and increased the overall flow of the water as well as the portion of that flow that pulled from the water heater, and now Amanda (and consequently the rest of us) are relieved.

In case you’re wondering why I didn’t take any cold showers, it’s not that I am just dirty and smelly (although I certainly am on occasion). So far I have taken all my showers outside, and the outside shower has not had any difficulty keeping a warm flow going.

Now that the shower problem is solved, we still have the issue of not being able to call for a trickle. We address it in roughly the same way most people would with a conventional water heater: we call for a full flow of hot water to fill the pipe, and then back it down to a trickle and pull from the water in the pipe long enough to get the job done.

The other issue that has been a little surprise to us is the time it takes to have hot water. We were careful to cluster most of the devices that consume hot water (utility sink, clothes washer, dishwasher, shower, bathroom lavatory, and kitchen sink) all in close proximity to the water heater. I was expecting almost instant hot water at all those locations, but I have been disappointed. It apparently takes a few seconds of burning for the tankless water heater to get the water up to temperature. So even though the bathroom lavatory is less than 10 feet from the water heater, it takes about 10 seconds after you turn on hot water in it before you feel the water getting hot. Certainly tolerable, but I had hoped it would be quicker.

The outdoor shower is further away from the water heater, so the wait for hot water is longer. I’ve learned to turn on the shower as hot as it will go and then to walk into the apartment to take off my clothes, and then to walk back outside to take a shower. By the time I’ve done that, the water is either hot or about to get hot.

The heater makes a slight noise. You can hear it clearly when you’re in the shop, sort of a low whooshing sound. Now that we know what to listen for, we can barely make it out when we’re standing at the bathroom lavatory and call for hot water there, but it’s not nearly loud enough to be distracting. I have my legal office set up in the shop, and I’m often on the phone with people while Amanda calls for hot water. The noise is never a problem. I welcome it, because it lets me know when we are burning propane.

The water heater came set for 120 degrees (F) output and could not be adjusted. When we were trying to figure out how to give Amanda a hot shower, one of the people at Rheem talked me through a change in the settings on the internal circuit board so I can now increase the output temperature, and we now have it set at 130 degrees.

Because the technology was new, Amanda was a little nervous about whether the water heater would produce enough to keep up with our usage. Our unit is the smallest one Rheem sells, designed for one bathroom. So far we’ve taken a shower while washing dishes and a shower while washing clothes, both with no problems. The next challenge, which we plan to do soon, is for one of us to shower outside and one to shower inside on a cold day, and see if the water heater can keep up with that. And in case you’re wondering, we already know who’s going to stop showering if it can’t keep up. I’ll make sure I have a fire going in the wood stove so I can warm my backside while Amanda finishes!

4 thoughts on “First Report on the Tankless Water Heater”

  1. Okay, we’ve now completed the two showers at a time test. Cold morning, two showers simultaneously calling for hot water, and no agonizing screams from cold water. It passed.

  2. I think you’ll find that keeping up with your usage will not be a problem in general, that is the specialty of tankless hot water heaters. You’ve already experienced the “wait”, which is what most people don’t expect – but once it’s going, it keeps on keepin’ on.

    Also note that tankless water heaters may be a good alternative for businesses as well as homes. Pubs, Restaurants, Hotels, Motels, and more, all use TWH’s for the very large cost savings, being able to expense or depreciate the up-front costs. So if you have an in-home business, or you just want to make points with your boss by cutting expenses, keep that in mind.

  3. I bought this product to attempt to be more “green” about our water usage. While the product ought to be able to do what it states, it is going back tomorrow. After installing it, we have been getting sizzling water within the cold water line (despite running the valve check they suggest within the handbook).

  4. Hi Wally,

    I’m not smart enough to tell you what could be causing that, but I can tell you that we’ve never experienced any heating of our cold water. I’m sorry you’re having this problem.

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