Alternative Plumbing Design Plans -- Which Is Better?

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DavidTu

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Attached is a PDF that contains two different designs for plumbing plans of a three-floor residence in Seattle. I would like your feedback as to which one will WORK BETTER for supplying hot and cold water without having to wait for hot water (recirculation) and without suffering temperature or pressure variations depending on what else is being used. I don't really care about the cost of materials or labor (as I am doing it myself).

There are two plans presented. The first plan is a Zone-run based plan where we are running many smaller (3/4") lines to each usage zone, then distributing from multiport tees. The assumption is that this design is better for simultaneous use as the pressure demands are in parallel rather than series. The recirculation in this design is more complex as 1/2" line are combined with check valves and balancing valves on the way back to the heater. (This design also allows turning off individual areas of the home for future repair work.) The second plan is a Loop-based plan and is our original plan that uses a 1" hot water loop covering most of the house (except for Master bath and detached Garage). The cold water doesn't have a similar loop for practical considerations of material use so it has a trunk and branch type design for the main and basement but uses the zones plan design for the upper-floor bathroom.

The designs are shown in Plan View (overhead) and all the floors are shown flattened onto a single plane with indications of the floor shown along with the room descriptors. Each floor (Basement, Main, Upper, Attic) is about 9ft high, but that is not indicated. The only area where we have "stacked" plumbing fixtures is the basement Laundry and the main floor Pantry (so the Pantry is shown as an "inset" in the layout. Various plumbing devices such as valves are shown using non-standard shapes that are all defined at the top of the drawings.

There are laundries shown for both basement and the upper floor, but in practice the upper-floor laundry will be used almost exclusively. The basement bathroom will not be used often for showering. We do expect the upper-floor laundry and the Kid's Bath shower to be used simultaneously at times on weekends. There is an 80-gallon indirect hot water tank that supplies most of the hot water for the house, with the exception of the Master Bath and Garage both of which are to be supplied by on-demand heaters. The master shower is to have 4x body sprays, a rain-head, and a handheld shower, only two of which (by type) are expected to be used simultaneously. The Master shower and bath are to be supplied with 3/4" valves.

This home is equipped with a fire sprinkler system that is only shown in part (it follows its own loop pattern on each floor with two riser interconnections between each floor). In order for that system to not become stagnant (and require annual testing) it is used to feed some fixtures, primarily the toilets on each floor (and the sink in the attic). The booster pump is needed for the sprinkler system, but also benefits the whole plumbing system as the pressure at the meter is an anemic 46 psi. We will increase the pressure to a maximum 80 psi using the pump. The water meter will be upgraded to 1-1/4" from present 3/4" copper. Note that 1-1/4" copper is about the same area as 1-1/2" PEX which is used for the line to the house. A 1-1/4" copper manifold will be built to distribute to the various plumbing and sprinkler runs for both plans.

There will be an irrigation system setup for supplying two hose bibbs on the home as well as sprayers, seepers, etc to water bushes, trees, vegetation, etc. Only the bibbs and the irrigation box are shown on the plans.

Fixture units are shown without adjusting for the 75% use rule for combined fixtures, except for the Master on-demand heater which is shown as adjusted. At the top of the plans you will see a table showing the various sizes for Pex pipe and the fixture units and GPM as specified by Uponor for its Pex-A pipe, which we are using.
 

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