Tankless Water Heater

Background

I needed to replace a very very old electric tank water heater before the bottom fell out and flooded my basement. I wanted to switch to gas for cost reasons.   I didn’t want to install it close enough to the chimney, which is far from all the plumbing, to use that as a vent and I didn’t want to put a hole in my roof for a water heater vent as a naturally vented tank heater would require.  That meant looking at a power vented model. Power vent models cost more, reducing the up front cost difference between a tank and tankless model.

I also have a general appreciation for the efficiency of not holding a tank of hot water at the ready 24/7, so between the two I was leaning toward a tankless heater.

I bought mine semi-locally from a plumber who installed, but then removed it.  Mine is the Home Depot Ecosense badged version: ECOH200DVLN.  Menards sells the Richards branded version.  Rheem sells the RTGH-95DVLN. As far as I know, they’re all identical.

My research indicated that this was one of the better (best even) tankless heaters available in quality, function and efficiency.  It is definitely overkill for what I need, and if I were buying brand new, I’d have gotten the 8.4 GPM version.  A few Japanese brands that got similar reviews, but as far as I could tell they were mostly internet order and didn’t have much for sales representation in the US.  All brands also made lower efficiency models, but they would have brought the same concerns as a standard water heater in requiring non-PVC roof venting.

Late in my research, I also discovered that there are apparently gas, condensing, tank water heaters which approach the same efficiency of around 93-95% but they are stupid expensive, like a minimum 50% more than the tankless version.

Installation

I installed the unit myself.  I’d describe myself as capable but inexperienced (as in none) in relation to plumbing and gas work in a home.  This was my first time sweating copper pipe (yes, I know shark-bites exist, but they’re expensive, I don’t trust o-rings and I’m an electrical engineer, so soldering things myself is a matter of pride).  It was also my first time messing with gas line.  I’ve worked a bit with PVC before, but it was in the potato canon capacity, not home improvement. So, I did a lot of reading and research before the install.

I bought most of the hardware, and did most of the install over a long weekend.  It took about two to three days worth of effort (steep learning curve for the soldering) and one or two returns to the hardware store as I had to make slight adjustments to my venting plans to better match reality (corner radii, clearance for 3″ PVC around bends, etc).

I did the venting with 3″ PVC.  I believe the instructions indicate you can get away with 2″ PVC, but only for an extremely short run.  My venting goes approximately 20ft to get to the back end of the house. There’s a total of 240 degrees of bend in each line. Rheem has guidelines in the install guide that list a max of 38ft, but I didn’t see anything explicitly stating if that was per vent or combined.  After some digging, I concluded it was per.  There are conversions for accounting for turns in that 38ft total.  I was within those limits, but just to be sure, I used some ‘creative’ deployment of a 60 and 45 combined to get a 90 degree bend plus an orthogonal step toward my wall.

The gas line coming into my house is 1″, which was fortunate given that the furnace which was the only existing gas appliance only needs a 1/2″ feed.  The water heater is a 199,000 BTU beast (over 4x the furnace) and requires at least 3/4″ gas line.  I think have about 35ft of 1″ line and then another 17ft of 3/4″ line to get to the heater.  This is on the edge of what’s acceptable according to the guides and I think falls somewhere just over a .3″WC pressure drop, but there were also tables for .5″WC pressure drop and I’m well within those.  I have two shut off valves in the gas line, one right on the heater (came with) and one in the gas line dropping to the heater before the union.  Nice thing about this is that it let me connect to the drip leg under the unit (between the valves) and pressure check all the joints right up to the very last one to the heater.

The location of the heater was selected to match the former location of the electric tank so I could reuse as much of the plumbing as possible.  Maybe it would have been a better plan to move everything 15ft closer to both the well and gas inlets for the house, but I didn’t and that’s only in hindsight.  These tankless heaters have the water in / out on the bottom instead of the top like a tank unit, so some wrap around plumbing was necessary. They make 18″ long flex lines for this, which I think aren’t a bad idea, but I decided to be cheap and plumb with the 3/4″ copper. Also, I suspect the ones i needed weren’t in stock, encouraging this decision.

I mounted the heater itself on some 2×4’s connected to a joist and stretching down to the floor.  This gives a bit of clearance behind the heater for the plumbing, kept me from having to use masonry bolts, and for whatever it may be worth, keeps the heater from direct contact with a relatively cold concrete wall. I had to move (lower) it once during the install, and having it mounted to 2×4’s instead of concrete definitely made that easier.

Success

Shortest section… After everything was connected and my construction mistakes fixed (mostly plumbing leaks, which are a pain to find and fix once water is in the pipes) the heater fired right up and worked flawlessly.  My well pump with all the taps in my house wide open can’t run enough water to outpace this heater – I could have bought the 8.4GPM model and been just fine, but I bought this one because I found it available at about half price.

More recently, I had the inspection done and passed (forgot to put the extension on the pressure relief valve, but that was just a note) so I guess that means I was successful too!

Thoughts on the heater itself

Speed to getting hot water at a tap is slower than with a tank.  I didn’t count before, so I can’t say for sure how much, but there’s *some* heat up time.

The so called “cold water sandwich” does still exist.  It’s not as pronounced as full hot to full cold and back to full hot, but it is there.  This seem seems to be a simple fact of life of the tankless heaters, but I believe that Rheem claims that this effect doesn’t exist, which is an overstatement.

The venting is powered, thus there is a blower and thus there is some sound.  The heater is mounted roughly under my kitchen sink, so I do hear the fan.  It’s not obnoxious, but it’s present.  I also have an indoor jet pump for the well.  That is much louder. Neither run unless water is being used, so it’s not like they kick on in the middle of the night (like a power vented tank heater would). Probably the most notable aspect of the fan sound is that it makes me aware that I had an occasional habit of turning on a tap with no regard for hot or cold if I was just rinsing something quick and never expected the water to warm up anyway (true regardless of heater).

I do find it a bit annoying that the flush valves aren’t included (the seem to be a minimum of $60).  It’s in the instruction manual that you need to flush the system yearly, and to do that you need the valves.  Seems like they should be included.  I think the outdoor vent terminations are not included either, but this is more variable based on install.  Both came with mine as the plumber I bought it from had the package ready to install.

In having to extend my gas line (1″ and 3/4″ black pipe), having to modify the plumbing (3/4″ copper), the venting (3″ PVC) and all the odds and ends to go with those, there was a lot of cost in the install – I’d say a few hundred dollars there and that’s not counting the hundred worth of valves and terminations that typically don’t come with the system. I think that with the loan of my Dad’s pipe threading wrench and borrowing a 3.5″ hole saw from work, I didn’t need to buy any major tools for the job. That said, I have a MAPP gas torch, a few pipe cutters, saws, hammers, drills, pliers, pipe wrenches, etc. all of which were used often.

The remote temperature control could be nice, but I don’t see much use for it in my situation, so it’s just wired up and chillin’ with the heater in the basement.

It’s going to be hard to say what the cost improvement is since I was going from a horribly old electric tank to a new, top of the line gas tankless, but it aught be an improvement.  I think the payback period, for me, is probably only a few years.

I will be curious to see how long the system lasts – not that I have reason to expect failure, but these are notably more complex than any tank heater I’ve ever seen with exception of the 95% efficient types mentioned earlier. I know that tank heaters are commonly rated at 6, 9 and 12 years and given the cost and mode of operation, I would hope that this would last at least toward the upper end of those timelines.