Questions tagged [tankless]

A tankless water heater directly heats water on demand, instead of maintaining a reservoir of hot water. Use this tag in conjunction with the [water-heater] tag

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Where should I install a Kolerflo 120W water pressure booster pump?

I have a tankless water heater and the water pressure is not enough to turn the tank on demand causing the water in the shower to be just barely warm. I purchase a Kolerflo 120W to boost the pressure, ...
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Okay to use cold water drain valve on tankless gas water heater as a spigot?

I need to use a pressure washer outside my house, but there's no spigot nearby. I do have my tankless gas water heater nearby though, which has drain valves (both hot and cold). When I opened up the ...
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Do I need to flush my tankless water heater annually?

I bought a Rheem tankless water-heater last year, it is RTG-95XLN-1 model. I was told that I need to flush it using vinegar and circular pump at least once a year, to prevent sedimentation. There are ...
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3 answers
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Heating water L-shaped house [closed]

I installed a tankless gas hwh but it takes forever to get hot water in two of the three bathrooms. I am wasting water. Any suggestions on how to fix this?
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1 answer
80 views

Do I need a 200 amp sub panel for my tankless water heater?

We are installing a tankless water heater that requires *3 50 amp 2 pole breakers. We are running new wire from the main breaker to a sub panel that will have those breakers in it and from there to ...
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1 answer
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Water heater tripping washing machine breaker

I just underwent a major renovation and now when my water heater is maxed out, it trips the washing machine breaker on its own dedicated circuit. I upgraded to 400A service with one of the 200A panels ...
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34 views

Outdoor direct vent tankless water heater (low nox) on exterior wall under overhang?

I have an exterior tankless heater that is one of the high-efficiency/low nox type, it has a direct vent (pretty small, actually) just sitting on the top grill. This is mounted outdoors, but is it ...
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Adjusting water heater that provides both domestic hot water and baseboard heat

I live in an apartment building with in-unit water heaters. Mine is a Weil-McClain Gold CGt gas-fired water boiler with tankless heater. It heats water for domestic use and also for my baseboard ...
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Noritz Tankless Water Heater Error Code 90

My noritz tankless sometimes shuts itself off with error code 90 - a combustion problem. I’ve had a plumber come out and service it since the previous owners didn’t for ten years. I still get the ...
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3 answers
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Rheem T-Rex 13 tankless water heater 6awg 3 wire 60amp

Can I run my Rheem T-Rex tankless water heater on same 60amp breaker as my 240v dryer? Can I put in a junction box at my dryer area and run power to the tankless water heater?
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Tankless water heater condensate

I have a Navien tankless and it drains outside. Does the unit run without demand? My concern is that the condensate could freeze upon exit and back up the drain. We use the house (NJ) most weekends ...
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2 answers
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How to connect 113A tankless water heater 125 feet from main panel?

Looking into ways to connect a tankless water heater that requires 3 40A double pole breakers and has 113A max draw 125 feet away from my 200Amp main service panel. Running 3 separate 8 AWG wires (...
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1 answer
188 views

Shower gradually cools, gets hotter when sink is on. Navien tankless whole house HWH

Our shower and a few other fixtures are behaving strangely. When I get into the shower it gets hot quickly and then gradually cools. But, I found that if someone else turns on a nearby sink (but not a ...
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2 answers
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Should I turn off a Tankless gas water heater during freezing weather if I cut water to the house during vacation

I will be away from home during freezing temperatures. I plan to cut the main water supply. But, I have a Rheem tankless gas water heater on my outdoor wall. If I cut the water supply, should I also ...
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4 votes
4 answers
1k views

Can/should I change GFI outlet to standard outlet

I am having my retirement house built. The house includes two RHEEM RTG-84DVLN-1 tankless water heaters that are plumbed in parallel. The instructions state do not hook up tankless to a GFI outlet ...
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2 votes
1 answer
95 views

How can I dampen a tankless water heater’s humming sound?

I just moved into our new home. First time with a tankless heater. I notice that whenever we turn on hot water after turning it off the tankless heater makes a humming sound. It seems like this is ...
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5 votes
2 answers
452 views

How to connect flex NMC to Rinnai tankless

I have a Rinnai V53DEP propane external tankless water heater. The manual calls for a disconnect, so I provided one. My plan is (was?) to have a flexible whip take all the wires (power and remote ...
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3 answers
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Water Heater (Tankless), Furnace, Chimney? What order of work? Different contractors?

PRIORITY 1: I have a 21 (yes 21) year old water heater (go AO Smith!) that I want to replace with a tankless water heater (live in MD). WANT 1: I have a chimney that needs to be lined and a fireplace ...
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1 vote
2 answers
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How to wire a double pole breaker with #6/2 AWG wire?

I'm installing a whole house tankless water heater and I'm a little lost as to wiring this power hungry unit and yes I'm upgrading to 200a service(by electrician). I've done some wiring before but not ...
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1 vote
4 answers
1k views

Tankless hot water smells

We bought a house with a Rinnai RUC98 tankless hot water heater already installed. We didn't notice anything about the water at first except only that when we did laundry, the dried clothes smelled ...
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Rinnai tankless on-demand water heater making a high-pitched whistling sound

I have a Rinnai tankless on-demand water heater. The unit is making a high-pitched whistling noise. I have: -Unplugged the unit from the electrical wall socket. -Turned the gas valve to the off ...
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1 vote
1 answer
28 views

No shutoff valve for tankless hot outlet

I just had a tankless water heater installed and I noticed that although it's recommend by the manufacturer, the installer did not add a shutoff to the hot water outlet. Will this cause any problems ...
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1 vote
0 answers
57 views

Trying to replace this leaking heater with a tankless, need help with the piping

Just moved into this house, South Florida, two stories, the heater is leaking and I'm replacing it with a tankless. I'm not sure how to plumb it since now I realized I have more pipes coming and going ...
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2 votes
3 answers
646 views

Replacing conventional: electric hot water heater with tankless

I have a 30 gallon electric conventional hot water heater that started leaking. It is in a cabinet above the washing machine; a tight fit: Since it is such a cramped space, I'm considering a ...
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2 votes
1 answer
149 views

Low flow bathroom appliance doesn't activate tankless heater

I have a whole house tankless water heater installed, and so far it's nice except one problem. I also have a nonelectric hot and cold toilet mounted bidet installed. Since a high pressure jet would ...
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3 votes
1 answer
322 views

Tankless water heater causes magnets (ceiling fans, induction oven) to hum while actively heating water

I replaced a tankless water heater with the same model, but a couple of years newer. (The original was damaged by careless house painters). This is a 13 kw Rheem unit and on its own circuit. Since ...
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0 votes
2 answers
188 views

Install Tankless water heater in the cold line

During cold season almost all the time we need to wait for hot water coming from the water heater to our faucets, showers etc. I want to install tankless water heater in the cold line as a ...
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2 answers
101 views

Can I use existing 40 AMP breakers when the item calls for 30 AMP

My tankless water heater stopped working and I purchased a new but slightly smaller one. The description on the website said that it used the same wiring as my last one (3 40 AMP breakers and 8/2 AWG ...
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Propane tankless heater before an electric one?

I am renovating a property that I use for a bed and breakfast. I have a fairly well working 30 gallon water heater that is electric. I also have a propane tank that I use for limited heating in my ...
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1 answer
239 views

Where is the 2 internal drain valve in Navien 240a tankless water heater (damaged needs replacement)

I have a 3 year old Navien 240a tankless water heater. A lot of water continuously flow through the condensation line even the heat exchanger is not operating. The leak can only be stopped when I ...
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-1 votes
1 answer
101 views

Adding a Tankless Hot Water Heater after a 40 Gallon DHW Tank to extend Hot Water Supply

I have a 40 gallon tank supplying hot water to 3 tenants (and sometimes their significant others) in 3 bedroom rental home. The 40 gallon does not provide sufficient hot water, so I would like to hook ...
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1 vote
2 answers
143 views

Can I convert 2 two-pole 60A breakers into 3 two-pole 40A breakers

Considering a new electric tankless water heater. But my 18yr old existing subpanel doesn't match what most new heaters use. Any help on the best way to go about this would be great. TIA UPDATE: ...
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1 vote
1 answer
80 views

New Rheem RTG-84-XLN-1 Error 12

I just installed a new Rheem RTG-84-XNL-1 tankless water heater. The unit has been throwing error code 12 off and on since it was first run. The manual and their tech support only entertain the idea ...
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0 answers
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How does a recirculation valve used with tankless water heaters work?

I understand that a recirculation valve will push cold water into the cold line from the hot line, until the water reaches a certain temperature in the hot line. But curious how does it do it? What is ...
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2 answers
150 views

Is a condensing tankless heater that expels excess water outside also a dehumidifier?

I understand that a condensing tankless water heater will recycle that extra heat and only vent the heat that it cannot use; this is why they have a greater efficiency. But the water that condenses ...
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1 answer
94 views

Do these look like good PVC exhaust and intake termination ends for a new tankless gas heater?

I just had a new tankless gas water heater installed, and it seems to be working well. But looking around here, other sites, and my own HVAC system, the terminating ends seem to come out further from ...
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1 vote
3 answers
139 views

Should I keep my 5-year-old electric tank heater as a storage unit if I am about to install a new gas tankless heater?

A plumber recently told me that its perfectly common to keep the old 40 gallon tank water heater in series with a new tankless water heater. The motivation is to decrease the time it takes to get hot ...
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1 vote
1 answer
409 views

Tankless Water Heaters in Series

I am building an addition with a basement underneath. The existing home is on a slab foundation, and the 20 year old tank water heater is in a closet. I was planning to replace this water heater ...
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1 vote
1 answer
77 views

Shower Runs out of hot water after a few minutes but sinks stay hot at the same time

I've just moved into a new house and my shower runs out of hot water after a few minutes. It's heated by a 10 year old Bosch tankless natural gas unit which I believe claims 105k output BTU which ...
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1 vote
3 answers
2k views

How can I mix tank and tankless hot water to feed my bathroom?

We are doing a master bathroom renovation and are considering adding a tankless hot water heater to supply just that bathroom. Our current 50 gallon hot water tank runs out after about 2.5 consecutive ...
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0 votes
1 answer
381 views

Installing hot water recirculating pump on a tankless water heater

I'm trying to see if I can install a hot water recirculating pump on my current setup. My understanding is that the pump sits just before the hot water line that goes into the building, but since ...
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1 vote
2 answers
587 views

Wiring size for 75-foot run from 40 amp breakers to tankless water heater?

I am planning out my future tankless water heater install. What type of wire will I need to use for a long run from my 40 amp breakers? Heater will be 240v and about 50-55 feet from the panel. I'm ...
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-3 votes
3 answers
702 views

Point-of-use tankless water heater electrical connection

Can I plug my new eemax SPEX3512 Point-of-use tankless water heater with these Specifications Volts: 120V kW: 3.5kW Amps: 29A Temp Rise F at .5 GPM: 48 Degrees Recommended Wire Size: 10AWG Into a ...
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0 votes
2 answers
601 views

Can I install a subpanel for an electric water heater next to the main panel?

I am replacing my A.O. Smith electric water heater with a Stiebel Eltron tankless water heater. This water heater needs 3 inputs of 40amp 125v. My existing A.O. Smith water heater is next to a gas ...
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2 votes
0 answers
122 views

Can tankless water heaters be mounted to the underside of joists in a crawlspace?

My single-story 1100 sqft home (1 bathroom + laundry + kitchen) currently has a gas 40gal tank water heater. We're looking to renovate and remove the tank water heater. It would be replaced with ...
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0 votes
1 answer
576 views

Rinnai R85 - no water pressure after flush

I have a Rinnai R85 tankless water heater. We recently had an issue with no hot water which was resolved by performing a flush. Since then, upstairs sinks and tubs are fine, but our two kitchen ...
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2 votes
2 answers
95 views

warm water only when we replaced the hot water heater with a tankless heater

We replaced the hot water heater with a tankless version. We now only get warm water from the faucets and showers even though the temperature is set at 140 0F on the heater and the outlet pipe from ...
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0 votes
1 answer
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Changing 240 tankless water heater to 120v tank heater

The wall is wired with 8/3. and the white was not used, capped in the junction box. The breaker box has two-pole 30 amp breakers. I want to change the wire size in the junction box to feed the 18a ...
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3 votes
1 answer
3k views

Installing a tankless water heater next to electric service panel

I am in the process of installing an outdoor natural gas tankless water heater. The issue I'm running into is clearances around the heater. There's a small spot on the back wall of the house where I'd ...
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2 votes
1 answer
2k views

Battery backup system for tankless gas water heater (outdoor install)

I have a Takagi T-K3-SP tankless gas water heater, which is installed outdoors. It still needs electricity though, so when I lose power at home, there's no hot water. The manual states it uses 86W ...
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