So I am going to be installing a rheeme tankless hot wanter heater, I was originally going to go with a 50 gallon, but as I have a whirlpool tub and my 40 gallon now barely breaks a third. My question is this. My gas line coming in is 1-1/4 all the way until it hits 2 t's that go down to half inch. 1 T pipe going to hot water heater and the other the furnace. I just read my meter and the meter stated it can do 250 cfh at 1/2 inch. Will this have enough gas to run a tankless without problems. The hot water heater I am looking at is [m.homedepot.com]

Thanks in advance

Been There, Done That. You will need a survey and evaluation of your supply and all the gas appliances operating from that service line. You may also need a utility survey from your supplies to be sure that they can supply you and your needs.

Gas tankless Heaters, use an enormous amounts of gas during startups and you don't want to leave yourself in the cold.

How will you capture the spill off from your tankless and where will it drain to? How aggressive is your waters and did you know that you may have to clean your tankless, twice a year, of mineral and scale? I'm glad you asked here, before you were sold a heater.

Best Wishes

The water heater will drain to a big wash sink next to my washer and dryer as that's how I set it up, I understand the cleaning that they need to go through, I do have a water softener hooked up to the house so that helps a lot. My problem I face is it's either a direct vent, tankless and power vent and with 4 people I already run out with a 40 gallon. I only have 2 gas items in the house furnace and water heater

Would an electric tankless be a simpler install, no worries about gas line being undersized and no vent needed.



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I would stay with the gas model. Can you draw up a isometric of the gas pipe system giving the size each pipe run and where it reduces and the length of each branch and main line from the meter at your home. 1 1/4" pipe carries a lot of gas but you should draw the system on paper and compute backwards from the gas fixture toward the larger gas lines in order to know how many BTU's each branch will support. Get a copy of a code book or you can probably find it on the web. It is easy to do and understand. Years ago before tankless water heaters I had a class on gas sizing and the instructor said at that time, that gas was generally oversized, in those days. I doubt that a tankless will require more than a pool heater and many of them run on 1 1/4" pipe size. If Tankless needs a generous amount of gas to start up, then the rules have changed. Post a drawing and I bet we can suggest a proper system for you.

I second PlumberLoren.

A simple drawing of gas piping with pipe size(s), lengths, btu's of appliances served etc.

Then we can offer more guidance.

I don't know how to upload an image but I can describe it. My gas line comes in from outside and makes an "L" shape. I designed it with the astricks but that is how my gas line goes all inch and a quarter except where the plus signs are those are the T's first t drops to hot water heater so it's converting 1 1/4 to 1/2 it continues to furnace in 1 1/4 and drops to 1/2 again and that's where it ends. Gas line has a plug at the last T. The first section is about 10 ft then does 90 degrees, after 90 there is 20 in then a T, after that there is approx 48 inches of tube and the last T. The only other appliance that uses gas is my furnace which is 60,000 btu. My current hot water heater is 40,000. Thanks for all the help guys

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Again, you have to add all of the btu requirement of any appliance using gas. Once you have that total, contact your gas provider with that number to determine if your supply is ample enough.

Options are: larger piping,or larger meter.


Best Wishes

The meter has to be sized for the connected load. That is not an "option". The piping is usually sized for a .5"WC drop maximum, again, not optional. I've only heard of one area of the country that is having problems with their gas supply and will not allow any additional load. That's in the Boston area, there may be more, but they are in business to sell gas.

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