Electric Water Heater Repair
Guide
Traditional Type
Circulating Systems
Cold Water Return
Type Systems
Plumbing Systems (Residential)
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Plumbing Systems (Residential)
Generally there are two basic types of plumbing system layouts found in typical residential piping, series plumbed and branched. There are of course, many variations and combinations of the two types.
The figure below represents a typical series plumbed system. I have simplified the illustrations showing only the water heater and sink type fixtures, leaving out showers, bath tubs, etc.
A series plumbed system means that the
water lines go from one fixture to the next, then from that fixture to the
next, etc. 
Branched systems are far more common.
The fixtures are shown in the blue prints, but how the piping gets to and from the fixtures is not shown. Normally, it's left up to the plumber to figure out the best way to plumb the house. Often this results in less than optimum plumbing layouts.
Even with identical floor plans there can be a number of variations in how the piping is laid out.
Often due to the hot water pipes being in a crawl space, behind walls, and in attics, it is easier to determine what kind of system you have through testing. This can be done by measuring how long it takes to get hot water at each fixture allowing the hot water to cool between measurements. Then run the furthest fixture till hot water arrives and then immediately test the other fixtures to see if hot water is nearby etc.
.