Supply Line Size

[hookerp]

I know the line coming in to the house reduces to 1/2 inch in order to keep the pressure even in the lines. If run a 3/4 line to a shower so it will have more pressure will it cause any other problems.

I am using the same pump to feed the house and the garage, but I do have two seperate lines comeing from the pump.

I am not worried about pressure drops in the garage, but this cause the pressure to drop going to the house.

[LazyPup]

A 3/4inch line is the code minimum for the main line entering a single family residential structure, however the line should also continue as a 3/4 inch line until it reaches the water heater where the inhouse water system is then divided into two parrallel but equal water supply systems, the hot and the cold.

Keep in mind that the capacity of a pipe is not determined by diameter but rather by cross sectional area, therefore a 3/4 inch line can carry twice the volume of a 1/2 inch line. For that reason all the lines downstream of the hot/cold junction should be 1/2inch lines to insure equal pressure. Running a 3/4 inch line past that point will often cause erratic pressure and introduce numerous other problems in both the hot and cold system.

While most shower mixers can be connected to either 1/2 or 3/4 lines, there is no advantage to increasing the line size as the volume of water passing through the mixer is determined by the diameter of the internal orifices, and is again determined by the actual diameter of the shower head orifice which is commonly a 1/4 inch or less in diameter.

Sinks are commonly connected by 3/8 inch supply lines therefore increasing the inhouse lines would again have little effect on their performance.

There are elaborate tables in the plumbing code to determine the required sizes of the lines, but unless the house is four or more stories high or has an excessive amount of plumbing fixtures above and beyond the typical one or two bathrooms, kitchen and laundry, their should be no reason to vary from these sizes, and just arbitrarily changing line sizes without computing the entire load for the structure will often result in many additional problems.