The first PATH Tech Set, "Resource-Efficient Plumbing" highlights five technologies that are easy to install, result in efficient and speedy delivery of hot and cold water, and allow for future, simplified retrofit of a greywater reuse system.
Goals of the Resource Efficient Plumbing Tech Set
- To decrease the cost of construction and maintenance of housing.
- To speed the delivery of hot water which minimizes the amount of wasted water because the fixture is not left to run until hot water is delivered to user.
- To improve the energy-efficient of water heating.
- To provide the opportunity for present or future greywater reuse.
Implementing the Tech Set
Vanguard and Zurn, manufacturers of PEX, plastic manifolds, and PEX fittings, publish concise installation guides that provide information about how to design, use, and install PEX and a manifold. A pressure drop chart, which will assist in the distribution system design, is contained in Vanguard's "Material Specifier: Tech Data" brochure.
Oatey's Sure-Vent Air Admittance Valves (AAVs) feature a chart that equates Drainage Fixture Units to valve sizes that are available, which assists the designer. The drain/waste/vent (DWV) system design is the same with or without AAVs, except that most of the vent pipe installation above a fixture is not needed and the vent stack end is capped 4-6" above the flood level rim of fixture/drain with an AAV that must be accessible for servicing. Note: One vent stack shall extend outside to the open air.
As with tank water heaters, tankless water heaters will require an energy and water supply. Units come with instructions for the professional installer to help them size the service utilities and locate the equipment. Electric tankless heaters will require more amperage than a tank heater. Gas tankless heaters will require electric, gas, and water supply. Power vent and out-of-doors mounted gas tankless units are also available.
Code Issues
Restrictive or non-existent codes prohibit the widespread use of some of the components of the Resource Efficient Plumbing Tech Set. These codes are discussed below.
PEX and Al-PEX
The 2003 International Residential Code (IRC) allows for the above-ground distribution of potable water if the pipe meets ASTM F876 and ASTM F877. Pipes must have a minimum diameter of 3/8" and be supported horizontally every 32" and vertically every 10' (vs. 12' and 10' for copper; or 3' and 10' for CPVC).
The same design constraints exist for PEX and Al-PEX as for CPVC and copper piping for the flow volume and other characteristics.
All plumbing fittings should be approved for use by the pipe manufacturer.
Because some stakeholders have opposed the use of PEX, it is advisable to speak with the local building official before your plan submission about the use of PEX, manifolds, and multi-zone distribution systems.
Plastic Plumbing Manifold
The manifold must be sized according to Table 2903.8.1 (p408, IRC 2003). Pre-manufactured manifolds should be tested, third-party certified and presented to each local code jurisdiction for approval. Parts for a manifold can be ordered from suppliers such as Sioux Chief and then assembled on site.
Low-Flow Fixtures
There are no code barriers to their use. Low-flow fixtures have been mandated by the EPA for over ten years. Fixtures that contain pressure balancing valves or anti-scald valves should comply with ASSE 1066 or ASSE 1016.
Air Admittance Vents
AAVs have been accepted by the IRC as long as they conform to ASSE 1050 or ASSE 1051 and the drain/waste/vent (DWV) system is designed with one vent to the outside (for venting the sewer system through the house). The outside vent can be wall-mounted.
AAVs must be designed into areas where they will remain accessible, such as inside sink vanities.
Tankless Water Heaters
Tankless water heaters should be UL-listed and certified by a third-party testing laboratory. Gas-fired units must meet all of the venting requirements of the manufacturer and the IRC.
Greywater Reuse Plumbing
Greywater reuse is not addressed in the IRC in its coverage of DWV systems. In states where water conservation is important and the reuse of greywater for irrigation is utilized, using a brown or purple colored pipe is a standard that is emerging to identify this type of effluent.
An active greywater reuse system should not be installed without consulting local code officials and/or the local health department.
Alternative Configurations
This tech set is your guide to a more affordable, energy-efficient and water-efficient water distribution network. It has been designed to maximize the benefits of each listed product. Since every project is unique, all five recommendations from this tech set may not be applicable. For this reason, we offer five alternatives to this Tech Set.
CPVC Water Supply Piping
Some plumbers and contractors may prefer to use CPVC pipes instead of PEX. When installing CPVC supply lines, use the tree/ branch style per prescriptive measures contained in the International Residential Code.
The rest of the features from this Tech Set are still relevant.
High-Efficiency Tank Water Heater
If a homeowner would prefer a tank water heater to their tankless counterparts, install an energy-efficient, quick-recovery tank heater with integral heat traps.
The rest of the features from this Tech Set are still relevant.
Plumbing without AAVs
In the off chance that local codes do not allow AAVs, instead design the drain/waste/vent (DWV) system with through-the-roof or gable end-mounted vent stacks.
The rest of the features from this Tech Set are still relevant.
Tech Set without Greywater Piping
If you prefer not to install a greywater DWV pipe design for current use or future retrofits, the rest of the features from this Tech Set remain relevant.
Hybrid Piping for House Larger than 2,000 Square Feet
For a home larger than 2,000 square feet, install an insulated tree/branch system to supply the mid-plumbing-run manifold for the parallel PEX or Al-PEX supply from that point to the fixtures. A hybrid zone system would also be efficient.
For larger homes, the rest of the features from this Tech Set are even more relevant than for smaller homes because the savings that they produce are magnified.
