tankless water heater - DIY Chatroom

jcash757 · 10-06-2009, 07:27 PM

I have a 1/2 line that goes about 30 feet from my meeter to my furnace. I am thinking of installing a tankless water heater that requires a 3/4 inch line. It will be downstream of the furnace. Can I just upsize the pipe where I T off the furnace to 3/4 inch line the rest of the way?

Thanks in advance.

Plumber101 · 10-06-2009, 08:08 PM

If off the meter the pipe is reduced down to 1/2" then you will need to resize the pipe for the complete systems.

Which basically means change out the 1/2 to 3/4 and then go to the tankless.

Provide me with the BTU rating for the furnace and tankless and I can size it for you.

I am piping a house that has a 100K furnace and a 180K tankless going 55 ft and I have to run 1" and more than likely you will to depending on the distance of run.

Also are you NG or LP

jcash757 · 10-06-2009, 08:25 PM

It's 1" leaving the meter then at the first T drops to .5" to the furnace. I'm NG and I also have a second furnace, tankless water heater, gas stove, grill, & fire place. I think a 1" T sound like the way to go.

Plumber101 · 10-06-2009, 09:23 PM

Tankless 180K
Fireplace 30K
Stove 30K
# 1 Furnace 100K
# 2 Furnace 100K
Grill 20K

This all speculation because YOU did not provide me with BTU ratings but, guessing you have 440K BTU you need at a min 1 1/4 pipe entering your house and feeding

A 1" pipe running 30' can serve only 374K
A 1 1/4" running 30' can serve only 768

Also by adding a tankless you might check with your local gas company to verify that the meter is sized properly

Need more info for proper sizing

What most people fail to understand that just simply adding a gas appliance can cause upgrading piping

jcash757 · 10-06-2009, 10:43 PM

The tankless is only about 3 feet from the meeter. I'll check demsions before I post anymore. I'm not were I can check now. Thanks again

Plumber101 · 10-06-2009, 11:42 PM

My advise is for you to hire a local plunber to do a sizing layout for you