Types of Residential Hot Water Piping Systems & Plumbing Diagrams

Explanations of the various ways that residential hot water plumbing systems can be laid out including plumbing diagrams

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Residential Plumbing

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Residential Hot Water Plumbing Systems

Basically there are only two 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. 

Looped or series plumbed piping

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.

When a home is plumbed in a series type or "looped" type layout such as the plumbing diagram shown below, it is ideal for using cold water return type hot water demand systems. One pump can provide fast hot water to all of the fixtures.   looped or series residential hot water plumbing system

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 since there is normally no diagram or blue prints of the piping layout for the plumber to follow...just the locations of the fixtures.

"Branched" residential piping systems are far more common.  

The branched system shown would need at least two hot water pumps to get fast hot water to all of the fixtures.

Typical branched residential piping layout diagram

Below is the plumbing diagram for another branched hot water piping system. As you can see some sinks share pipes for part of the distance, and some for another part etc.  It is difficult to use a single demand pump for such a system.

Branched residential piping system diagram

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. 

Run the furthest fixture till hot water arrives and then immediately test the next closest sink to the water heater to see if it gets hot water faster, and then the next.

Let the piping cool for an hour or two and repeat with a different location as the furthest fixture.