Tankless hot water heater
 

Just curious if any of you have experience with tankless hot water heaters?

Looking at putting in a direct vent condensing model so that it will exhaust with pvc out the side of my house rather than up through the roof. We added a bedroom in the basement and the flue runs through the room. I think it will save a little money in the long run too, but thats not the most important reason for us.

My heat and ac unit already exhaust out the side and this would go in that same room.

As I read installation instructions it tells how to much natural gas in needs so now I am wondering if a larger pipe/meter will need to be installed.

I have also been told that you need to have a water softener to keep it from scaling and clogging.

Any input? I try to do as many things as I can myself, but may do the water softener and new water lines myself and leave the install of the water heater to a pro.





Randy





Randy

You need at least a 3/4" gas line depending on how far from the meter your heater will be. Those heaters are hungry when running. As far as a softener, it all depends on if you have hard water or not. The other option is about half the price is to get a direct vent hot water tank style. It vents out with pvc as well. Just depends your preference. I personally don't care for the tankless. They require a hot water valve to be fully open for it to kick on, and there is a delay before you get hot water. Also, you have to be really careful picking one out because to get the water as hot as you may want, means they decrease the water pressure. Another issue for instance, we just replaced our kitchen faucet. No matter what you remove in that faucet, it's low flow. Our hot water tank heater is less than 10 feet away, and it takes forever to get hot water to that faucet. I can actually get hot water faster to the upstairs sink that isn't low flow and has probably over 50' of pipe the water has to run through. That issue would be even worse with a tankless.

I put a propane one in 5 years ago and love it. I think mine is rated at 9.5 GPM and you will never run out of hot water. I went into the extended menu on mine and cranked the sucker up super hot.

I think it may take a little longer to get the hot water to the faucet but who cares, water is cheap.

Mine is a Rheem/Ruud 80% unit that uses a metal vent. I wish I would have picked up the 90+ model but my plumbing sales guy talked me out of it...probably because he didn't have one. I had to run 3/4 pipe to mine also. You can also get one that mounts on the outside of your house and don't have to do any venting. My stove is also propane and I have to fill my 125 gallon tank about 2 times per year at about $150 each time.

I have had no issues out of mine and only cleaned it one time since I installed it. I pumped vinegar through it for about 1 hour with the heater turned off.

When I go out of town I turn the propane off to mine (and the water to the house). I don't what would happed if you had a hot water line rupture and that thing pumped out 150*-160* water all day long.

I put a tankless in the last house I had. I'd do it again in a minute. All the issues people complain about can be solves easily. (Like low flow. That's just the end on the faucet, so change it out.) We have hard city water, and I never had to clean it in at least the 8 years or so I lived in the house with it. (It's still in the house I know because my ex wife lives there. :BlahBlah:) They are fantastic. But, yes, they are gas hungry. I did have gas pressure issues at the house after installing it, but ONLY when the furnace in the house, water heater and the furnace in the garage were all running at the same time. I had to learn to shut off the furnace in the garage before I got in the shower or it would really cool off. :biggrin2: I needed a larger meter/regulator. I had run large enough pipe, but the regulator wouldn't flow enough to keep up. My local gas company would have to switch it out. Don't let the gas company con you though, they will try to tell you that you have to go to a "commercial" meter. You tell them that's a crock of sh!t! Residential is residential, they just have to give you a larger regulator or meter. BTDT before.

Thanks for the posts guys!

I think from what I am hearing I will be OK. I have 1" gas line coming in the house and only have the furnace and hot water heater, so I may be ok there as long as the meter can keep up.

The one I am probably going to get is a Richmond/Rheem 9.5 gph and I really don't have a big house.

I live in a 1920 house and all the electrical had been replaced before we moved in but still had original plumbing. I have replaced about a 1/3 of my pipes with pex and will replace all of it when I do this. It will be nice to have all new pipes with water softener and filter. Just want to make sure this hot water heater is done right and will probably do everything but the hooking up the unit and venting it myself. Just a little nervous and want to make sure its right!


Thanks again and if anyone has more to offer, please do!




Randy

So if you are replacing with pex, are you running to a manifold or with the home runs? What size pex are you using? It's all going to make a difference in how your tankless performs. 1/2" pex is only going to get about 2.5gpm flow. 3/4" pex could get you about 4.5gpm.

As far as the low flow, it's not just a nozzle on the end of the faucet for kitchen faucets with the pull down nozzle. They have a small diameter hose that is used on the pull down part, and it severely restricts the flow. Nothing you can do about it. It's easy to check. Turn on the faucet full and fill a gallon container and time it to see how many gallons per minute flow you get. The biggest flow will be from the bathtub faucets, those would be 4gpm+. The pull down kitchen faucet you will be lucky to get 1.5-2.0gpm. Which means twice as long to get hot water. Then you need to check the specs of your tankless to see how many gpm of flow it takes to activate the burners and make sure your lowest flow faucet in the house is enough to turn the burners on. The shower heads are the lowest flow usually, unless you take the restrictors off.

You a plumber taylorjm?

In my younger days. Spent 10 years as a plumber/pipefitter until I started to see how bad it wore my dad's joints out and decided I didn't want to do it for the rest of my life.

The other thing you mentioned is that you are looking at a model that vents out through pvc pipe. Be aware, by using a power vent model like that is going to cause you even more of a delay before getting hot water. When you turn on a faucet, the flow sensor calls for hot water, but first, an exhaust blower has to turn on and ramp up, then a vacuum switch has to activate to show there's enough exhaust flow, then the burners light, then water can be heated.

What's the reason you are looking at a tankless? Is it because you want to take a 5 hour shower? Someone takes a lot of baths in a huge tub? Or is it because it will save money?

Taylorjim, I plan to do 3/4 to a manifold with 3/4 to the hot water heater. 1/2 out to everything else.

One of the big reasons for the tankless and direct vent is to gain some room where the hot water heater is and eliminate the flue pipe running through a bedroom I built in the basement. We are going to add a half bathroom in the room that houses the heat/ac and hot water heater. I live in a old small house.

But, I do want to make sure I do everything right.


Randy

Yup, we did the same thing. We had an attic converted to a bedroom and it had the old metal flue pipe from the furnace and hot water tank. Furnace was replace and vented out pvc, so went with a 50gal power vent tank water heater and vented that out through the side of the house to eliminate the flue vent.

You need to run 3/4 out of the water heater, then reduce just before going to each faucet. So, if the plumbing is under, reduce just before comING up through the floor. If you don't, you won't have enough flow. Maybe you meant that....
I'd feed the water heater with whatever size comes into the house. If it's 1", feed it with 1".

Taylorjm, every tankless I've ever seen has a combustion blower and every gas/propane furnace does as well. You will never get the efficiency without it. I think the delay to fire is about 1/2 second and you will never notice it. I can run my kitchen faucet at any temperature from warm to scalding hot and the unit fires every time. Why keep 40 to 60 gallons of water hot all day long when it is not needed. I also moved mine from a hall closet to under my crawl space where it is out of site.

I still tell my wife every time she is washing dishes to try and keep from turning the hot water on and off every time she rinses a dish. I'm not sure if it hurts anything but it cycles on and off every time she rinses.

Yes J-mech, I am pretty sure I have 3/4" coming in but I was planning on 1/2" out of the manifold. My 3/4 goes down to 1/2 now in the main run and I have plenty of flow and pressure. My current lines are a combination of black pipe and galvenized. My house is from 1920 and the part I have already replaced with pex had about a pencil size running in the middle of the pipe.



Also, while I have your guys ear. I need to do an expansion tank and not sure where in the line that should go.



Randy

Expansion tank can go anywhere.

Randy, I'm telling you, if you run out of a tankless heater with 1/2" you won't have enough flow. You need to run like I said. Sure, you think you have good flow now because a tank water heater doesn’t need flow to give you hot water. Tankless requires flow to operate the burner. Besides, I wouldn't even recommend running 1/2" out of a tank either, but people do. Then they set it up really hot, because of the restriction.

1/2" pex will just about fit inside 1/2" galvanized btw...

Truth be told 3/4" pex has only slightly larger ID than 1/2" galv. for a few reasons. First being that the I.D. of 1/2" galv is larger than 1/2". Its actually closer to 5/8" but not quite. The OD of 1/2" hard drawn l,m, and k copper, cpvc AND PEX is 5/8".

SECOND...Cross linked polyethylene is pretty robust, however it needs more sidewall meat for expansion and general durability than copper does. Because pex was put in the CTS family for easy compatability with hard drawn copper tubing and cpvc, it has to maintain the o.d. to work with various fittings such as compression and shark bite. So.... thicker sidewall + same out side diameter = reduced i.d. for pex tubing.

When sizing, depending on elevation and f.u. 3/4" is used at very minimum for the main. Most of the time we use 1". 1/2" definitely has a place, just use enough sense to know what/where it is.

Edit, never understood the logic behind a hot water heater. I mean, why buy a water heater to heat already hot water? I myself have only seen regular old water heaters meant for heating "cold" water, but people always talk about these hot water heaters and I have never seen one. Its a mystery to me :bigthink:

J-mech and Rescue are spot on about the 1/2" pex. By the time you put a fitting INSIDE the pex. your really restricted. Compared to 1/2 copper that doesn't have a fitting inside it. If you don't have enough flow, the burner won't kick on.

Oak, you are talking about a combustion blower on a furnace, those are usually on the 80% efficient ones. When you get to the 90% condensing and use pvc pipe as exhaust, there's an exhaust blower that has to run longer than 1/2 second before the burners kick on. A furnace that exhausts with pvc will usually have a 20-30 sec purge before the burners kick on because that's required to verify enough venting to not push carbon monoxide back into the house. Now figure, this tankless is going to consume about 3-4x as much as your furnace, and you don't want that to not vent properly, so the exhaust blower has to run at least a few seconds before the burners kick in. How many seconds? I honestly don't know. But I'd worry why my furnace running at 60,000btu needs a 20 second purge, and your going to run a 200,000btu tankless heater that would only need 1 second purge. I'd guess it's going to need at least 10 seconds, but again, I am not positive. Maybe they are different technology now, could be, I don't know, but I'd want to check that before buying one.

Now, as far as being efficient. You really need to look long and hard at this one. People think if they aren't storing hot water, they are saving money. There's tons of studies out there that say you need at least 10 years to break even with a tankless because of the higher up front cost. That's assuming you don't have to repair the tankless. If you need to vent with pvc, like I did, a tank style water heater will run you about $800-900. A high end tankless could run double that. So, you need to make up about a $900 upfront cost in gas savings. Many people have had tankless installed and said their bill didn't change. So your going from running 40,000btu tank style, keeping water warm all the time, to a 200,000btu tankless that runs when you need it. I guess it just depends how much water you use, how soon you will recoup the cost. All I know is when those burners kick on, and you hear the whooooosh of all that gas being burned....ya gotta wonder how much it's going to save you! All depends on your situation.

Also you mentioned you have 3/4" water coming in to the house. That's 3/4" either copper or galvanized, which is much larger and has much better flow rate than 3/4" pex. Like rescue said, I'd use 1" pex for the mains if you have 3/4" coming in now.

Ok, now its clicking guys. I did not realize the size difference. Will do 1" in and maybe out to the faucets as well.

This is why I asked here, I knew we had some pretty fart smellers! :biggrin2:



Thanks guys!





Randy

I too have been wondering about these things, as within my utility room things are cramped, as it is now, I have to pull the hot water tank to access the furnace.... my A coil clogged up (result of owning Black Labs that shed like crazy for so long, nother story) and I had to pull it at 3AM when it was -10*F outside earlier this winter, it is a PITA to drain 40 gallons of hot water, un-plumb and re-plumb it back in besides dragging it out of the way, and back into place.... a tankless would clear up floor space for me around the furnace.... maybe I could have kept up on keeping things clean better,

as it stands right now, I have to pull the hot water tank again, during that few weeks we usually have where we don't need either heat or AC in late spring so that I can reinstall that A-coil so that I can have AC this summer.....

Ok, I gotta ask. Why would your a-coil get clogged up with dog hair? The coil should be downstream of the filter, so it should be on the clean side of the air flow.

Unless there wasn't a filter....... :bigeyes:

Seen it many a time.:bash2:

oh yeah, there were filters... never "not" a filter in place.... this is a counterflow (downdraft) system, system is 19 years old, 1 year less than I have lived here---- probably 8- 10 years ago, I had to do the same thing/// though it wasn't -10* outside at that time, it was cold enough to need the furnace to work, I had a little more time to mess with it as the house wasn't cooling off as fast as it was on that -10* night between last Christmas and New Years.... but that other time that the furnace started acting stupid since it wasn't as cold out, I could take the time to pull the cover and clean the coil.... still had to pull the water heater then....this time it was faster to just cut the lines and yank the coil, reassemble and relight to get the wife off my behind because the house was cold...
we have been dog-less since about last Turkey day, 1st time since we moved in here. my son bought his own home and took "his" dog with him...
(still got 2 cats to put up with though) hopefully once winter and also spring rains are behind us I hope to get another....

but now back to talking about tankless water heaters...

one thing that I was wondering, can I just plumb the exhaust into the furnace exhaust, like my current tank type water heater is set up?

Taylorjm, I'm a commercial HVAC tech and know all about pre and post purge. I'm pretty sure mine fires off in few seconds max and I will see if I can time it soon.

I pulled a 50 gallon electric water heater and replaced a 9 SEER heat pump with a 16 SEER one and you are correct, I did not notice any change in my power bill. I'm not sold on all this efficiency crap.

I installed my own 9.5 gpm Rheem unit that was around $1300 at that time with the valve kit and tax. Looks like Home Cheapo sells it now for $1199.00 + valve & tax. I also had to run 60' of 3/4 black iron pipe when I did the install so that would add to the bill if you are paying someone. Yes, they run more money but they free up space and that is what I needed. I will never go back to a tank type, but that is me.

Not to change the subject or steal this post but I have no experience with pex, what do you people think about it? I was a copper only guy until I moved in my current house 17 years ago and now I'm sold on CPVC.

Not likely.
What type of flu is the furnace? Less than 80% with a double wall pipe? How large is the flu? Most tank water heaters are around 30,000 BTU, and the tankless are well over 100,000 BTU, if not 200,000 BTU, so it's not likely that the furnace flu is large enough to be able to handle the exhaust. Plus, if you get a 90+ water heater, it will vent in PVC. If the furnace you have is 90+ and vented in PVC, no, you cannot put two power vented exhausts into the same outlet. First of all, its illegal. Second, you run the risk of backflow. :beerchug:



I like it on remodels of old houses where there isn't a lot of room, or risk of freezing. It's easy to run, and works as well as PVC. Would I do new construction with it? Heck no. But it works good as a replacement. My personal preference (on new construction) is also copper, but I've done a lot of (C)PVC, and it works just fine. I just don't like the funny taste for the first few months. You just can't go wrong with copper. Plus, it seems to last forever. But it's sooooooo expensive!

I am learning a great deal. Thank You!!:popcorn::popcorn:

You need a dedicated flue for tankless.

The tankless type also pull combustion air from outside.

On the 90+ it is a separate schedule 40 PVC pipe.

On the 80+ the intake is in the same pipe as the flue exhaust. IIRC the intake is in the outer pipe and the exhaust is in the inner pipe.

Personally, I would use copper, just because it has been time tested to be reliable. Pex would be next on my list, but I'd have to research the best kind of crimpers/clamps again and see how they are holding up. I don't care for cpvc for water supply lines. I just don't trust glued connections for pressurized pipe. I know the cement isn't really a glue so to speak, but I just would worry one of those joints wouldn't get applied correctly. Just my opinion.

I'm not arguing....
But I've seen just about as many copper lines that didn't get soldered right as I have PVC fittings that didn't get glued right. Seen copper come apart, seen PVC come apart. One time, I saw a 90° copper elbow blow the outside corner, because the plumber didn't deburr the pipe after cutting. It was on a hot water circulation line, and the rolled edge caused cavitation to orrur in the elbow, eroding it out. That was a new one for me....
I've also seen pex fittings blow off, iron and galvanized rot out..... so, they all have issues one way or another, lol.

They sure do all have their pluses and minuses. Had a 90 blow off on a circulation line? Like, a boiler with a whole 15psi on it or a high pressure boiler?

No, the 90 didn't come off, the elbow eroded out and it sprung a huge gushing leak.
It was on a hot water line, as in hot water, not cold. House was huge, so the hot lines ran a circulation pump back to the tank to keep hot water in them at all times. No waiting for hot water that way. Only had to travel from the already warm line up the wall to the fixture. :beerchug:

Gotcha. I read it as the elbow blew off because the pipe wasn't reamed out.. couldn't figure out why that would happen. Caused a pinhole leak from not reaming it out, yup.

Ours goes out tankless is what we’re going to install!