Pipes, Threads & Flow
Most plumbing for shower heads in U.S. houses is standard 1/2" NPT (National Pipe Thread). It is a tapered thread that seals as the male/female threads tighten. Most plumbers recommend using Teflon plumbers tape or pipe sealant compound for a leak free joint. Some shower heads and plumbing fittings, as well as most hoses and handheld showers are 1/2" NPS (National Pipe Straight - threads). While Teflon tape or compound is still recommended, the joint must also have a washer between the male and female threads to seal. A shower head with NPS threads will work fine on a pipe with NPT threads. A shower head with NPT threads will not usually thread far enough onto a pipe (or other fitting) with NPS threads.
One problem that can occur when installing a shower head or fitting with NPS threads onto a shower pipe with NPT threads is that the shower head washer must have a flat surface on the end of the pipe to seat against in order to seal. Many shower pipes are very thin walled. This leaves little wall thickness to create the flat sealing surface needed. When installing the shower head with the washer, instead of seating, the washer is forced up inside the shower arm pipe. It is necessary sometimes to create a flat surface on a shower pipe. A grinder or file use on the end of the pipe to remove burrs and sharp edges and to create the needed flat surface will usually work fine. Do not over tighten the shower head when installing.
Many customers confuse themselves by measuring pipes. Common sense says that all you need to do is measure the outside or inside diameter of a pipe and you know what size pipe it is. Sorry, that's not correct. In fact, the 'size' of a pipe does not refer to either the inside or the outside diameter of a pipe or a fitting. A 1/2" pipe has an outer diameter (O.D.) of 0.84". A 3/4" pipe has an O.D. of 1.05"
Flow Rates for galvanize pipes in gallons per minute
Flow Rates for copper pipes in gallons per minute
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Shower head cleaning instructions, click here. (New window will open.)
