How to Add a Length of Pipe to Water Pipes

Pipe Sizing

• 1

  Estimate the water volume in gallons that the new section of pipe will carry each day. For a domestic residence, use a figure of 70 gallons per day per person.

• 2

  Contact your state Department of Agriculture to find typical water usage figures for farm animals or irrigation. Estimate the daily water usage in gallons for each piece of equipment that is installed. Consult the user manual or contact the equipment manufacturer to find the typical usage for each item.

• 3

  Divide the daily usage by two and note the answer, which is the estimated peak flow rate through the pipe in gallons per hour. Divide the peak flow rate by 60 to convert to gallons per minute.

• 4

  Select a pipe sizing chart for the type of pipe that you intend to use. Copper and plastic pipes are common in domestic installations, while commercial premises often feature steel pipes. Read across the bottom of the chart until you reach the peak flow rate that you calculated. Rule a line vertically up the chart from this point.

• 5

  Follow the line up the chart. If the peak flow rate is more than 35 gallons per minute, skip this step. Otherwise continue until you reach the intersection with the line, sloping downward from left to right, that corresponds to a water velocity of 4 feet per second. Drop back down the line that you ruled until you reach the closest line, sloping upward from left to right, that corresponds to a specific pipe diameter. Note the diameter indicated by the line, which is the minimum pipe size that you should use.

• 6

  Use a different procedure if the peak flow rate is more than 35 gallons per minute. Follow the line that you ruled up the chart until you reach the intersection with the horizontal line that corresponds to a head loss, or pressure loss, of 4 feet per 100 feet of pipe. Drop back down the line that you ruled until you reach the closest line, sloping upward from left to right, that corresponds to a specific pipe diameter. Note the diameter indicated by the line, which is the minimum pipe size that you should use.

Pipe Joining

• 7

  Check the size of the existing pipe that you will be joining to the new length. Establish whether you can join the new section to the end of the existing run. If not, you must insert a tee into the run.

• 8

  Install the new section of pipe into your premises in line with your plans. Route its free end to the position of the joint with the existing pipe. Close the shutoff valve on your system to isolate the existing pipe run and open the drain valve to empty it.

• 9

  Remove the end cap from the existing pipe if you are joining to the end of the run. If not, skip this step. Cut through the pipe if the end cap is glued, soldered or welded in position. Clean the end of the pipe and remove any sharp edges. If the new pipe is the same diameter as the old pipe, fit a suitable straight coupling to the end of the pipe. Otherwise fit a reducing coupling that accommodates the different diameters. Fit the coupling in accordance with the manufacturer’s instructions.

• 10

  Cut through the pipe if you need to insert a tee into the run. If not, skip this step. Select an equal tee joint if the new pipe is the same diameter as the old pipe. If not, select a reducing tee to accommodate the different diameters. Check the datasheet for the tee and make another cut in the existing pipe to create a gap that just accommodates the tee. Loosen the clamping brackets that secure the existing pipe and install the tee. Retighten the brackets. Fit the tee in accordance with the manufacturer’s instructions.

• 11

  Join the end of the new pipe to the coupling or tee, whichever you fitted. Check that all the connections are sound and that both pipes are secured in position. Close the drain valve and open the shutoff valve. Check for leaks.