Tank or tankless water heater for 3-family home?
After finishing extensive renovations to the owner’s duplex, we’ve realized we need to upgrade the water heating system for the entire building. The water’s currently heated via an old oil boiler, which isn’t the ideal situation in the summer or when the two rental apartments are occupied (which will be starting May 1st!). We’ve spoken to several plumbers about installing either a gas-fired tank system (A.O. Smith 75 gallon) or a tankless (Navien NPE-180), and there seem to be tradeoffs involved in either. For the time being– due to budget overruns on the earlier renovation– we’re keeping the oil boiler, though we may look to do a conversion in the fall. Would love to get people’s thoughts on the better option here…
If we went with the tank, we’d install a leak tray underneath and a leak shutoff sensor. It would be vented through the chimney, next to the other vent for the oil boiler.
If we went tankless, it would have to be vented outside, so we’d have PVC piping running up along the exterior wall. We already have a small backyard, so we wouldn’t necessarily want to reduce the space further.
Whatever option we went with would need to be sufficient to produce adequate hot water for a 3-family home (3 dishwashers, 1 washing machine), for about 5 people.
Guest User | 4 years and 3 months ago
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Master Plvmber | 4 years and 2 months ago
So, that’s why you’re seeing savings. Families who use tankless water heaters throughout the day typically don’t see fuel savings with them. The long periods of inactivity are where seasonal efficiency is gained.
ceci | 4 years and 2 months ago
Empty nesters, no dishwasher but washer/dryer yes. I pay $116 quarterly for water!!!
Master Plvmber | 4 years and 2 months ago
Ceci, what is your usage like? Is this water heater working for a family? A single? Is it used during the daytime or is the house typically empty?
Guest User | 4 years and 2 months ago
Definitely helpful. I have encountered water warming to be slow even in traditional boiler and tank systems if the pipe run is a floor or more.
ceci | 4 years and 2 months ago
Your welcome!!! Glad to be of assistance if I can.
Guest User | 4 years and 2 months ago
thanks for sharing.
ceci | 4 years and 2 months ago
I have a Bosch tankless water heater installed and have mixed feelings. On one hand, u utilize quite a bit of water before it warms up and that’s not so good when u pay for water. However, in the spring, summer and fall my National Grid gas bill is significantly less; therefore this is a pro to this system…..
Guest User | 4 years and 2 months ago
Half the people I talk to sing the praises of tankless and the other half say it’s a bad idea. I understand that a lot of the above comments are from plumbers who do this every day so I would trust them. Multiple subs told me they have tankless and they haven’t complained about them. Net net becomes confusing to decide. I did install a tankless and will see how it pans out. The vents are not huge and if you run them along the back wall it may not be so bad. But there are rules about how far the vents need to be from lot lines, windows etc.
BklnRefugee | 4 years and 2 months ago
My experience with tankless (outside of NYC) confirm what Chris Petri says. I spent multiples of my energy savings on maintenance.
lkrshacmzcy | 4 years and 2 months ago
The Engineering Plans and Permits alone would run your cost too high for a true seeable Return on the efficiency.
I think Tankless Units are awesome but the way New York was built and is currently governed, they are cost inefficient to install outside of a Renovation that already has an Engineer on payroll. Even then, the skilled trade to service those units, which is a totally different skill than installing, is high due to the low pool of qualified Experts.
lkrshacmzcy | 4 years and 2 months ago
The Engineering Plans and Permits alone would run your cost too high for a true seeable Return on the efficiency.
I think Tankless Units are awesome but the way New York was built and is currently governed, they are cost inefficient to install outside of a Renovation that already has an Engineer on payroll. Even then, the skilled trade to service those units, which is a totally different skill than installing, is high due to the low pool of qualified Experts.
wjbehrle | 4 years and 2 months ago
We recently used Richie at Sessa Plumbing & HVAC for this. We needed the space in the mechanical room in order to do some needed repairs/replacement of our HVAC unit, and losing the old water tank was the only option we could figure (after half a dozen HVAC folks tried unsuccessfully to offer any viable solutions). We had some trouble with the unit (Navian) early on and Richie had to replace it (on Navian’s dime, of course), but he’s incredibly professional and I trust him more than any other tradesfolks I’ve worked with. We did need to get an engineer and expeditor for the job (Richie helped arrange). It was a very costly job, but we’re happy about it. The only thing I’ll say from a user’s perspective is that I have to wait longer than I’d like for the hot water to come through, in the winter at least. The first person to shower might have to wait close to a minute for the water to run hot. But, on the flip side, you never run out of hot water!
Guest User | 4 years and 2 months ago
I would tend to lean toward the conventional tank type…for a tankless you would end up running stainless z vent or polypro for the venting which is not going to be cheap, unless you can meet the specs for stubbing it out on the back wall which is pretty hard to do on a brownstone. I think that an AO Smith 75 gal should be sufficient, but as per your one plumbers recommendation, if there are space constraints, a pair of smaller units plumbed in parallel is a good option. An indirect could work, but if you are considering an OTG conversion in the fall, it seems unwise since you have no hot water during the switchout
hkapstein | 4 years and 2 months ago
It’s very hard to find a decent plumber for something like this. I think Eman137 might be worth talking to.
Guest User | 4 years and 2 months ago
Thanks for the very detailed info, Urbandad. I have a slight concern about the chimney vent, since it was the chimney cleaner who first suggested going with a tankless model to avoid having to put a second vent through the chimney (though he didn’t say that it couldn’t be done). To give more info– and to respond to anotherposter’s question– three different plumbers all independently suggested 75-gallon tank if we went with a tank (though one said if there wasn’t room for it, he’d recommend two 50-gallon tanks linked together, and another said we could even go with a 65-gallon commercial high-efficiency tank). I’m not terribly concerned with why the previous owner didn’t add a gas water heater because the building had been rentals for decades and they neglected numerous improvements and repairs (many of which we only discovered mid-renovation, of course).
I might look more into adding a storage tank or indirect to the current oil boiler; I was actually going to have an oil fuel company person come out to take a look, but their office came down with Covid and we never r escheduled; and the current fuel company I use just had terrible customer service and never got back to me about sending someone out to present oil-based options! All the regular plumbers who weren’t affiliated with an oil company suggested switching to gas, and we’re running out of time because I want to get this all settled before the tenants move in…
anotherposter | 4 years and 2 months ago
Is a 75 gallon tank enough for 3 units or it a 75 gallon/unit?
hkapstein | 4 years and 3 months ago
If you put a tankless condensing boiler/water heater you’ll technically need an Alt2 permit with plans filed by an engineer or architect, unless you had substantially the same type of equipment already. You can replace a boiler or water heater with the same type of boiler under an LAA filed by the plumber, but that wouldn’t normally apply to a condensing boiler replacing a conventional one or an oil to gas conversion. New gas service would require a bunch of other filings, and if you have that filed, just have your architect amend the plans and schedule B to show the boiler you desire.
It’s true you can technically vent a direct vent boiler into the back yard, but requirements for venting them at least a certain distance from windows and doors etc and the practical fact of not wanting noxious fumes in your yard makes it almost impossible in most brownstone setups, so you’d need to run the vent to the roof. I’m not sure you can just run a plastic vent for a condensing boiler up the back of the building. The condensate could freeze in the winter. There may be a workarou nd for this, but I’ve never seen anyone do it that way.
Here are some options, you could add a storage tank to your water coil in your boiler. The tank calls for heat and the boiler heats it up and stores it so the boiler can have longer cycles. Add a thermostatic valve. Easy to do unless you have a recirculation loop for the hot water, which it doesn’t sounds like you do. You can likely do this with an LAA(plumber’s permit only).
Stand alone electric or heat pump water heater. Also LAA.
Indirect water heater. Probably LAA.
You can do a new standard gas water heater on an LAA as well, but the plumber will need to get a chimney approval, which may or may not be an issue in your situation.
A condensing gas water heater(tankless or tank), as I understand it, cannot be done on an LAA and would require an Alt2 filing. Can you vent non condensing oil and gas in the same chimney flue, and is your chimney large enough for two appliances? Who knows, but if the previous owner didn’t set it up this way, there may be a reason.
At the end of the day, oil is an expensive fuel and heating up a big boiler to make hot water with it is not going to be efficient. A standalone electric or gas tank unit is probably your best bet. Gas is cheaper, but you need to confirm the chimney is suitable. Can you put a tankless non-condensing gas unit on an LAA? Possibly. But I suspect there will be a problem with the chimney if you try to vent that many btus along with the boiler up the same flue.
Guest User | 4 years and 3 months ago
Cate, yeah, that’s part of the reason why we didn’t consider an oil-to-gas conversion initially– when we first bought the house, National Grid still had that moratorium on any new gas hookups/conversions. We were able to eventually get gas service turned back on, and then got distracted by the rest of the renovation and didn’t realize that we might have hot water issues until we had actually moved in and, well, had some hot water issues! The “boil boiler heats the water” system isn’t terrible in the winter, but it takes some time to fire up in the summer when the boiler isn’t constantly running; and the boiler also wasn’t well maintained and it’s actually missing a thermostatic mixer, meaning you have to be VERY careful when you use the hot water, since it can come out scalding hot. We’re definitely not thrilled that the plumber and contractor didn’t point that out while they were replacing all the plumbing in THE ENTIRE BUILDING…
shahnandersen
in General Discussion 4 years and 3 months ago
I’d go with the 75 gallon tank. I would also recommend that until you replace the oil burner, you run the domestic water output from the oil boiler into your new heater instead of bringing in cold water to refill it. That will save you some gas usage during the heating season (you can turn off the boiler during the summer).