Thanks. So our house is not as big. It's 4000 sq ft with 5 bathrooms and 6 people. We do have a whole house softener but not the filtration. We are on city water. My plumber said since we have the softener we won't have to do the annual flushing of the system. He didn't say anything about an app or recirculating. I'm not very knowledgeable about how it works. But there is a line in the quote that says "install new recirculating pump."

I'm getting more bids, but that was just the first one.

I'm wary of using Home Depot because I find that they do not send good installers. We used them a few times in our old house and they did a terrible job on the installation, had to come back several times to fix leaks, left trash in the attic, and one installer fell through the ceiling into my kids' room. Then to fix the hole, they sent another terrible worker who didn't patch properly and a terrible painter who didn't know how to texture a ceiling. The whole experience was bad.

We put in a tankless in our attic 8 years ago from a standard one in a closet in a hallway and have never looked back. It has been great. it services our master bath and our two boys bathroom.

We have another in the garage that services the kitchen, daughter's bath and utility that we will replace with tankless when it is time. It too, will go in the attic. The pricing for two seems inline with what our one will cost, as we have to add some electric (I think an outlet though ours will be gas).

ssdarb: And I had Home Depot install an OTR microwave and he did a fine job. So what? One cannot draw conclusions from an anecdote re one installer from a company that operates nationwide. And one can hire someone else to do the work; or do it himself.

I’ve had a tankless for 24 years. I would never go back. You will still need to clean it occasionally, even with a softener. It will just need it less often.

Thanks everyone for you replies. Lawrence, I find your last response unhelpful and kind of aggressive with the italics and the "so what?" comment.

But thanks to everyone else.

Cook's Kitchen,

So the plumber told me that because we have a whole house softener, we don't have to flush it annually, but I'm the type that would probably want to know how and do it annually anyway. Is the cleaning/flushing difficult?

Flushing is done by disconnecting the tankless from the incoming water supply and the output to the household plumbing, placing cleaning solution (either vinegar or a commercial product) into a bucket, connecting a small recirculation pump to the tankless inlet and a hose from the outlet into the bucket, and running the pump to circulate the solution through the unit. Some tankless installations are done with bypass valves to facilitate cleaning, which eliminates the need to disconnect the inlet and outlet lines from the heater. There are example videos on YouTube.

The price that you have been quoted is high on both the tank and tankless.

You want to be sure that any installer uses Service Valves so that you can easily clean it when you need to.

The plumber is correct - you will have to clean it much less often - 3-5 years -- with a softener.

There are good videos on cleaning them on youtube as Dadoes said - I made up a my own cleaning kit and just keep it together near the heater - so it takes about 30 minutes to do.

Jake, thanks. We put the project on hold til after the holidays. So what is "Service Values?" On waterproofing a shower I had to read and understand the TCNA handbook. Is it like that, an industry publication? I'm a nerd, so I read all this stuff.

They are"Service Valves" not "Service Values". They allow you to isolate the heater from the rest of the plumbing and circulate vinegar when it comes time to clean it.

They also provide a place to put the pressure release valve and provide unions for disconnecting the water to remove or replace the heater.

Not at all going to knock Rinnai, I've just used Rheem and they work well. They have a low activation flow rate and seem to have a lot of other issues worked out.

I agree - get the largest one (which is generally 200k BTU input for any of these).

Most of these can vent through the sidewall, which solves any roofing issues.

Other than that, it should a standard roof boot if it goes through the roof.

You also need to call the gas company and get an evaluation of your gas service's ability to handle the BTU load of a tankless water heater. You may not have the service needed to support one or two new gas tankless heaters. A 200K BTU tankless draws much more gas than a standard tank water heater when its running.

The gas company can use different pipe sizes and pressures to adjust for the upgraded BTU requirement, but sometimes upgrading pipe sizes can get complicated because they are embedded in framing and hard to access.

Bruce

Keeping an eye on this thread-I've wondered for a few years now, about switching.

I had several plumbing companies here and all of them told me different things. Some said I need 2 tankless units installed, some said one and done, some said one plus some kind of extender thing. It's frustrating bc there is no consensus at all, and they all say their approach is the right one.

Ok, so let's do your math:

-In what part of the country do you live? (what we are trying to get to is the coldest the inlet water will be)

-How many showers do you anticipate using at the same time? (not the number of bathrooms).

-Are there any extraordinary large uses of water (big soaking tub, for example)

Let me know the answers to these questions and I can give you a pretty good idea.

Thanks for your reply.

Location: We live a little north of Houston, TX It does freeze here, but not very often and usually not a hard freeze. When it does freeze, it generally warms up to over 32 during the day and then might freeze again at night. Last year we had a few 15 degree nights where it did not warm up for a few days, so it was below freezing for maybe 4 or 5 days. That is unusual. There have been lots of years where there is no freeze or only a very mild one for the whole winter.

Showers at the same time? I'd say 1, 2 and sometimes 3. Probably averaging 2. We have 4 kids, but since they are in school sports, they shower at school during the week. It would be unusual for everyone to be bathing at once, I don't think that has ever happened. My girls share a bathroom and also my boys share a bathroom. They told me that if they shower back-to-back, the second person runs out of hot water if the first person took a long one.

There is a big soaking tub in the master bathroom, but it is not used very often, maybe twice a month.

Other info that may or may not be helpful:

- we currently have 2 regular hot water heaters. One of them serves 3 bathrooms and one serves the master and an office/guest bathroom.

- we have a really nice master shower, and we both tend to spend more time in there than we should. When it was a crappy shower, we were in and out in just a few minutes because it was so nasty. Now that it's nice, we tend to linger longer.

- the house is really wide, so there is a lot of distance for the water to travel. I think that's why one of the plumbers said he'd recommend 2 units, and one recommended the extender thing (which I don't remember what he actually called it - it might have been a recirculating pump, but I'm not sure).

- there are 5 bathrooms, but one is a 3/4 downstairs that serves as a powder room and only gets showered in if we have a bunch of guests.

- we don't usually have a bunch of guests, so there are not that many times when there are extra people showering.

- we have a whole house water softener.

- I got lots of different answers about how long we'd wait for hot water. We wait now however long it takes for the cold water to run through the pipes and for the hot water to arrive. So waiting is not really a big deal. But I got lots of confusing input from the plumbers about the wait time.

- I asked all the plumbing companies about leaks, auto-shut off, drip pans, etc. I got all manner of different answers ranging from: it can still leak and not stop, thereby ruining the house; it can leak but the drip pan will catch it and an alarm will go off to alert you; the drip pan will catch it and it will automatically shut off; etc, etc. I want to eliminate the many gallons of hot water sitting on top of my head while sleeping, that's the main motivation for thinking about changing to tankless.

- I finally do understand recirculating pumps (I think), but that also seems like a potential damaging leak situation since the pipe that the recirculating is happening in seems like it is essentially your new "tank" in your tankless system. Unless it is doing it's recirculating on top of a big drip pan with an auto-off function, I don't see this as providing an advantage over my current tank heaters.

Ok, let's start with the math first:

We are going to assume a cold water inlet temp of 50 degrees minimum.

You need to raise that to 105 for a shower. I'm going to bump that number to 107 since you will have heat loss in your pipes. That's a 57 degree temp rise.

A condensing, 200k BTU tankless unit will heat about 6.5 gallons per minute (gpm) at that temp rise (any make or brand will be the same). 200k BTU is about the largest residential unit made.

A single shower is 2.5 gpm.

You could run 2 showers at the same time plus 1 faucet in the winter time on one heater when the inlet water temp is 50 F. If the inlet water was warmer than that, you would be able to run 3 showers at the same time. I would say that one tankless heater is right on the edge of being ok for your household. The "spread out" issue may tilt it in favor of using two.

A tankless heater adds about 10-15 seconds on to the wait for hot water. In your situation, where the heater is above, rather than below (in the basement) the additional wait would be closer to 10 seconds. In the basement, the heated water from a tank heater rises and keeps hot water in some of the lines - thus reducing the wait a bit.

You can add (or use a built-in) circulation pump to reduce the wait for hot water. If you don't have this already, it's best to have a dedicated return line. If you do this, your hot water lines REALLY need to be insulated, including the dedicated return. Otherwise you will be using a lot of energy keeping the pipes warm AND you will be removing that heat with your air conditioning in the summer.

As for leaks and such: Any plumbing anywhere can leak. A tankless heater is no exception. A tankless heater won't have 50-100 gal of water in reserve - so there's that.

You can set up a tankless heater with a drip pan and drain. You can also set up leak detection and a main shutoff valve. I haven't seen a tankless unit leak yet, although I'm sure they do - because any plumbing can leak anywhere. I think they are inherently less likely to leak than a tank however.

I think that if you are worried about water dumping then simply replacing your tank heaters every 12-15 years would solve that problem instead of waiting for them to fail. You presumably don't wait for your tires on your car to blow out before you replace them... why would you do that with your water heaters?

Before you go much further with the idea of tankless, you should confirm that your gas service will support a 200k BTU appliance. Assuming your current heaters are gas (40k BTU) you will need to be able to supply another 120k BTU. You will almost certainly need to run a new gas line up to the attic as well (probably 1").

Just to say, a consideration regards to showers is whether the tap is turned full-open during use, whether that 2.5 GPM shower flow rate occurs. I find the spray from a full-on shower is too strong, too much overspray and water spattering around. Also, I have hand-held shower so I can pull it down and direct the spray instead of it going around outside the "target" area.

I checked my tankless a few mins ago after a shower (one running). It showed (LCD panel) flow rate of 1.4 GPM initially. I left the water running after I finished to check again ... 1.0 GPM (rinse-off flow), input temp 67°F, setpoint 103°F, display reported operating at 19% of capacity at that moment. Electric unit on a 120a circuit. Weather has been in a warming trend for a couple days, next norther blowing in tonight with 31°F predicted for a couple hours in the mid-morn.

I realize my usage patterns aren't typical, compared to a family with children who ... uhhh, perhaps can't so much be constrained on usage habits.

I live a little west/south of Houston area.

I understand that some people may not use the shower full on. I also know some people pull the water restrictor out. But when you are putting numbers to things, you really need some accepted design standards. Showers at 2.5 gpm and 105 are what we design to unless we know for a fact that it's not that (such as in California 2.0 gpm).

The water inlet temps are a little trickier - but 50 being the coldest is a pretty safe bet in this situation.

Design, of course, must be built around standards. People asking questions about tankless get alarmed when told that they can't run two simultaneous showers, which isn't always the case in real-world usage vs. design standards.

I'm on well water. My pressure tank is in my garage, so is protected from direct weather exposure, but the incoming temp can drop lower than 50°F during an extended cold snap.

Thanks to all for your replies.

Jake,

What a wealth of information. Thanks! I am continuing to read and learn on this subject. We will make a decision fairly soon, but it's not urgent as if the tanked ones are leaking or anything like that. Thank you so much for taking the time to put together that explanation.