Announcement

Announcement Module
Collapse

How To Post Images

Want to know the how to upload images to your posts? Image Posting Tutorial
See more
See less

Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts

  • Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

    Hi,

    I would like to replace my broken old 50-gal tank water heater with a tankless one (Rinnai R75Lsi). I had 2 plumbers who gave me estimates for the job. Both of them are rated 5 stars on the Rinnai website. However, their proposals for gas line connection are completely different. I am wondering if anyone can answer my questions regarding the gas line.

    My existing gas line has a 1 1/2 inch diameter and runs 40 feet from the meter before splitting into smaller lines to my gas appliances: gas stove & double oven (less than 80,000 btu), gas furnace (125,000 btu), and my old water heater (40,000 btu).

    The new Rinnai with a max. 199,000 btu will bring my total max btu to 404,000 btu. The two plumbers told me how they would provide gas for the new Rinnai:

    #1: Add another gas line from the Rinnai all the way to the meter and request the gas company to provide a 2 PSI Split meter system to provide proper pressure for the Rinnai while keeping the furnace and stove & oven on the old (low pressure?) line.

    #2: My existing 1 1/2 inch gas line is enough to provide up to 650,000 btu. Therefore, all I need to do is to request that my gas company upgrade my meter to 425 CFH.

    I suppose choice #1 will definitely work for the Rinnai, but the 2nd gas line going all the way to the meter proposal costs a few hundreds of dollars more than proposal #2. Does anyone know if #2 will work just fine for all appliances or not? Does adding a new 199,000 btu water heater to the original line affect the performance of the furnace and stove?

    Any comments/suggestions will be greatly appreciated.

    Thanks.

    Onlearningcurve

  • #2
    Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

    Assuming you have 2 PSI at the meter I would recommend the split meter and a separate line also. But it's not my money.

    Go with option #2 and upgrade to a larger CFH meter. Be sure he brings at least a 3/4" line off the main to the heater. Fire all gas appliances at the same time and check manifold pressures. If everything is within spec you're good. If a gas valve drops out then just add the second line to the meter. .

    Remember, that Rinnai won't be running at 199,000 btu's all the time (if ever).

    Confirm with Washington Gas if they will upgrade you to a split meter at no charge.

    Comment


    • #3
      Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

      We can't accurately tell you if your system will be okay with a new meter without measurements to each of the appliances and the pipe diameter to the water heater, assuming that is where you will be putting the tankless.

      Either get a third estimate or call each of the other plumbers and ask about the other method.

      Comment


      • #4
        Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

        As Easy said,
        We need all B.T.U.'s and lengths to them to size accordingly.I just re-plumbed the entire house main to provide enough Cubic Feet Per Hour(Per UPC Chart).

        Thank goodness the Father in law of customer understands the necessity of things being done right.
        Who knows,I may have lost the job to the lowest bidder running 20' of gas flex.

        Comment


        • #5
          Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

          Originally posted by drtyhands View Post
          As Easy said,
          We need all B.T.U.'s and lengths to them to size accordingly.I just re-plumbed the entire house main to provide enough Cubic Feet Per Hour(Per UPC Chart).

          Thank goodness the Father in law of customer understands the necessity of things being done right.
          Who knows,I may have lost the job to the lowest bidder running 20' of gas flex.
          I have had customers who want to add a line to the kitchen or porch for a grill or range. When I get the chart out and tell them I have to start at the meter with bigger pipe they usually show me out.

          Comment


          • #6
            Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

            Thank you all for the kind help.

            I have been trying to contact Washington Gas to find out how many PSIs the low pressure line supplies. However, the person I am supposed to call wasn't in yesterday. I will try again today. I have also asked a third plumber to come to give me an estimate today. I will be sure to ask those questions you suggested.

            Here is a more detailed description of my current gas lines:
            --------------------------
            My gas line from the meter (275CFH) is 1 1/2". This line runs about 45 ft before spliting into two smaller lines (I think both are 3/4"):

            One of the two 3/4" will run about 10 ft to the old waterheater gas inlet. The max. 199,000 btu Rinnai will be installed at about the same location.

            The other 3/4" line goes almost 4 ft and then split into two 3/4" lines, one of which goes 10 more feet to the less than 80,000 btu stove & double oven while the other goes about 6 more feet to the 125,000 btu furnace.
            --------------------------
            Is this enough information to calculate if the Rinnai can get its required pressure of 5" w.c. to 10.5" w.c.?

            Thanks again,
            Onlearningcurve

            Comment


            • #7
              Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

              The lady at Washington Gas said that my low pressure/normal pressure line is 5" to 7" wc. The Rinnai needs at least a 5" wc.

              If I don't add the new line, would the gas pressure at Rinnai be 5wc even if all of the stoves, ovens, furnace, and Rinnai are on?

              Comment


              • #8
                Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                No way to know that until the Rinnai is fired up.

                Does your gas meter have a regulator mounted just before the meter? If so, you should be good to go. If not, you may want to consider replacing the 50 gallon heater.

                It's pretty unusual to have a 1-1/2" gas line for the btu's you currently have.

                Lanham, Md is a little outside our service area but if you can't get the answers you want I might take a look at it.

                Comment


                • #9
                  Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                  Thanks. You are right to think that the 1 1/2" gas line is unusual. I just went to measure the diameters and I believe it is only 1" diameter. Sorry, I did not make measurements until now because the guy who gave me the quote #2 told me and wrote down that I have a 1 1/2" diameter line coming in.

                  But my measurements are: the line from meter to split only has an outer diameter of 1 1/4" and the lines after split have outer diameter of 1". So their inner diameters are probably 1" and 3/4".

                  Does that mean I should go with quote #1 and put in a new gas line at 2 PSI for the Rinnai? It will cost me about $430 more than quote #2 before 30% tax credit, so maybe $300 more after the 30% tax credit.
                  Last edited by onlearningcurve; 06-24-2009, 03:58 PM.

                  Comment


                  • #10
                    Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                    Yep, you need another gas line back to the meter or upsize the existing one you have now. Either way, you need a meter changeout so might as well go with a 2 psi split.

                    I don't know if either plumber discussed this with you but there is another option.

                    Change the current meter and existing gas line to a 2 psi system. This will require a pressure test be put on the whole system and 2 psi regulators at each appliance but no need to cut drywall or add a second line all the way back to the heater.

                    Good luck,

                    Bill

                    Comment


                    • #11
                      Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                      Thank you so much. I asked plumber #1 and the Washington Gas lady about using one single line with 2 PSI and, yes, the Washington Gas lady mentioned that a regulator for each appliance will be required. Plumber #1 just said it would be a trouble to deal with this situation.

                      Are regulators expensive and expensive to put in? Because this method means I will need 3 regulators. Or can the furnace and stove share one regulator since they have a 4 ft segment of common line before the lines splits to two?

                      Comment


                      • #12
                        Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                        there should be no reason why you can't run a new 1'' or 3/4'' gas line back to the meter and tie in just as it leaves the meter. very common here and i'm also talking 400,000 btu pool heaters.

                        we don't typically get medium pressure inside the building unless it's a new job site and we don't want to pipe larger than 4''

                        200,000 at 40' is just over 3/4'' with 1/2'' w.c. drop.

                        so i'm at 1'' here.

                        1 '' dedicated line to the heater is my choice. forget all the regulators that need to be vented out.

                        rick.
                        phoebe it is

                        Comment


                        • #13
                          Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                          $40-$50 for a 1/2" regulator, double that for a 3/4" one. About 1/2 hour or more to install one. It's best to have one at each appliance but not necessary.

                          The double oven will be the hardest one to install no doubt.

                          It's only more trouble to find and repair leaks on the existing gas line you didn't know you had.

                          Comment


                          • #14
                            Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                            Originally posted by PLUMBER RICK View Post
                            there should be no reason why you can't run a new 1'' or 3/4'' gas line back to the meter and tie in just as it leaves the meter. very common here and i'm also talking 400,000 btu pool heaters.

                            we don't typically get medium pressure inside the building unless it's a new job site and we don't want to pipe larger than 4''

                            200,000 at 40' is just over 3/4'' with 1/2'' w.c. drop.

                            so i'm at 1'' here.

                            1 '' dedicated line to the heater is my choice. forget all the regulators that need to be vented out.

                            rick.
                            Rick,

                            It doesn't make sence for the added labor and materials to install a second line all the way back to his heater if it's not needed. Not to mention the additional cost of drywall and paint repairs to hide it. 2 PSI piping inside houses is very common here.

                            Venting regulators to the outdoors is not required here either. All that is needed is a leak-limiting device installed on the regulator. Most come with one installed anyways. He will need 2 tees installed at each regulator for testing and adjustment.

                            Comment


                            • #15
                              Re: Gas line/pressure question for Rinnai tankless water heater installation (R75Lsi)

                              so now it poses another question.

                              why replace your leaking 50 gallon water heater with an expensive tankless that requires maintenance and a new gas line and venting?

                              what's wrong with another 50 gallon heater?

                              here we go again

                              rick.
                              phoebe it is

                              Comment

                              Working...
                              X