Tank-less questions


Old 08-02-17, 12:01 AM
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Tank-less questions

Hello, I have been researching this for several weeks did seem so much of what I see on the Internet is somebody trying to sell their product so I found this form that I wanted to try. Im looking to convert my propane gas tank type water heater system that is in an interior closet to a tankless unit and had a few questions had a few questions.

Im trying to get a feel for how much longer it will take to get hot water at any given fixture. From the instant the unit senses demand how many seconds does the unit take to be sending water and at its maximum temperature rise capacity? Also about how many seconds would it take to send water at say half of its temperature rise capacity? Like the tank water heater this tankless unit will also be propane gas.

The indoor closet that my tank water heater is presently in is about 2.5 x 4. Will I be able to use some of this additional space created with this tankless unit for storage such as for brooms, mops and other equally maybe somewhat flammable type items? Can this closet now be carpeted?

As it is now there is an 8 x 14 vent in the door leading to the closet from a hallway and a 6 x 14 vent on the ceiling to the attic. Will this be enough for this tankless unit? This original water here closet does not have an exterior/perimeter wall so can I use the original 3 inch vent that runs to the roof for venting the tankless unit? Do all interior models require a drain as this could be a real problem here. Thanks
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Old 08-02-17, 12:24 AM
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Welcome to the forums.

I am not a plumber or the plumbing pro. Just some observations and opinions.

Tankless heaters should be the best thing to happen to water heaters. As it turns out.... they are and they aren't. They do supply how water on demand and don't need to store it.... saving on heat loss thru the tank. However, they are much more expensive than a basic water heater and they require more expensive servicing especially in areas with high mineral content.

The lag time from demand to delivery should only be a few more seconds than your standard hot water provided. The specific rise is different for every unit and is part of it's specs. The more you pay..... the more hot water you get faster.

As far as the closet.... it could have rug as the unit hangs on the wall.

I'm not sure if all units require a drain.

Here's a biggie...... a lot of the units are direct vent which means you can't use that 3" flue line. The exhaust type would need to be confirmed by reading the manufacturers specs.
Old 08-02-17, 07:38 AM
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My son got one a year ago and it does provide endless hot water. However, the electronics are hair trigger sensitive. It would not operate reliably until he isolated it on a dedicated circuit. The initial install tapped into an existing circuit and it required continual resetting. I just don't get the $4-5000 cost for a unit that requires annual back flushing by a pro. My 50 gallon Rheem is in its 12th yr without a glitch and my gas cost is under $20/month.
Old 08-02-17, 11:33 AM
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so can I use the original 3 inch vent that runs to the roof for venting
Unlikely. Tankless water heaters require special (expensive) high temperature venting materials not your usual type.
Old 09-01-17, 04:48 AM
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Tankless water heaters are very common in Europe and Asia, in particular Japan. They are great however many people have reservations.

Gas units are very powerful with high capacity although less efficient than electric units and require exterior ventilation. It depends on where you live as well, if you live somewhere with very cold incoming water temperature then you heater will need to work harder and be less efficient. I'm a member of another forum where a guy had just installed a Rheem unit and was on track to save $200 on bills within the first year of installing.
Old 09-01-17, 11:38 AM
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Generally speaking, tankless units are better on paper than in real life. They tend to work best in warmer climates where the incoming water is warmer.

Never dealt with one with propane but the natural gas units often require more gas than the existing piping can deliver.
Old 09-01-17, 01:47 PM
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Look into the Navien model 240 tankless. I've installed many of these units with pretty good luck. Venting on them is via a 3" solid core pvc pipe. 100' minus about 6' per 90 degree bend. 199,000btu so the size of your gas line would be a big factor. Naviens come with a kit taped inside the cabinet with spare parts and a gas conversion kit for propane.

With all that said flow rate depends on temp rise and navien has this chart in the specs. Unless you have a custom shower with multiple heads or body sprays you shouldn't have an issue.

The model 240A is about $150 more and has a built in re-circ pump if need be. Thats the best feature imo.

The cost of the unit is about $1400 plus venting.
Old 09-01-17, 02:10 PM
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Phil, welcome to the DIY forum. Most of us "regulars have a less-than-stellar opinion of tankless water heaters and especially so of electric models. Your opinion sounds like advertising whereas most of us have, or know someone, with real-world experience. There is most definitely a place for the tankless water heater but in most residential applications they fall short of a tank-type in more than one category. I'd list a few now but I need to go lie down.
Old 09-02-17, 03:36 PM
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My opinion is based on having good experiences with them and being a fan, just trying to give some info.
Old 09-02-17, 05:01 PM
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Umm, beings your email addy has to do with tankless water heaters, I'd say it's more than experiences and being a fan!
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