6 Easy Steps to Line Sizing

Line sizing seems like it's complicated, but once you break it down you'll see that it really isn't that hard. This tutorial will make you a line sizing expert!

Step 1.

First things first. Figure out the total BTU demand for the job

Adding up the BTU/hr the appliances are going to need. You can find this information on the appliance's nameplate. Be sure to calculate extra for future appliances.

In the example above, we see a vertical tank powering a room heater, a water heater, and a clothes dryer. Make a simple sketch like the one below to help visualize what needs to be done.

Step 2.

Measure the distance between the regulator to the furthest appliance.

In this example, the furthest appliance is the clothes dryer and the distance between it and the regulator is 84 feet.

Step 3.

Add up the BTU from the three appliances.

The room heater is 30,000 BTU, the water heater is 38,000 BTU, and the clothes dryer is 35,000 BTU. These numbers add up to 103,000. That's how much capacity the line needs to handle between the regulator and the building (a to b).

Step 4.

Figure out which pipe you'll need to run between the regulator and the building.

Since this job is using an integral twin stage regulator we'll turn to Table 3 – Second Stage or Integral Twin Stage Pipe Sizing. The type of regulator you use will determine the table you'll need to figure out your line size.

In this case, since we need to run a total line of 84 feet you'll need to the column for 90 feet (highlighted in yellow below). You always want to round up.

Next, run down the column until you find a number greater than your total load (The numbers are in the hundred thousand so the first number in the 90 feet column, 33, is actually 33,000). The total load is 103,000 BTU so we'll stop at 185,000 (highlighted in green below) being the first number greater than 103,000.

This means we'll need to use 3/4" pipe (highlighted in blue below) because it can handle up to 185,000 BTU.

But why not use the 7/8" copper tubing which can handle up to 161,000 BTUs (as shown in image below)? Once you go past 5/8" in copper tubing it's safer to use pipe instead.

Step 5.

Determine the size needed between the room heater and the water heater (b to c).

We're beyond the line for the room heater so its BTU is no longer taken into consideration. Now we'll add up the BTU for the water heater (38,000) and the clothes dryer (35,000) to find the demand on this section of the line is 73,000.

Back to Table 3. Run down the 90 feet column until the number is greater than 73,000. In this case, we can use the 3/4" copper tubing or the 1/2" pipe.

Step 6.

Figure out the line needs for the rest of the job.

To the clothes dryer (c to d) we need to support 35,000 BTU. According to the table, we can use 5/8" copper tubing or 1/2" pipe.

To the room heater (b to f) we need to support 30,000 BTU. The table shows we can use 1/2" copper tubing or 1/2" pipe.

To the water heater (c to e) we need to support 38,000 BTU. The table shows we can use 5/8" copper tubing or 1/2" pipe.

And that's it. Line sizing couldn't be easier. Be sure to check out the Rego LP-Gas Serviceman's Manual for more examples and a listing of the other tables.

Need something more visual? Watch our 6 Easy Steps to Line Sizing video.