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FEATURE
A larger perspective on tiny houses
By
Enrique Gonzalez
When you hear the phrase “ tiny house ,” you may imagine a tipi tent house , an igloo or maybe a treehouse . But , unlike these structures , tiny houses are constructed similar to larger homes with basic necessities such as a water supply and drain system .
David Viola , IAPMO CEO
In the spirit of the sharing of unique experiences that shape the plumbing industries in our respective nations , the following article looks at health and safety provisions for tiny houses . Written by IAPMO Plumbing Code Development Administrator , Enrique Gonzalez , it is the next in a regular series of similar articles that will run in this magazine .
Advancements in material , craftsmanship , and plumbing have allowed tiny houses to resemble larger homes with all the bells and whistles while still maintaining a small footprint . A common question that comes to mind is : What are the code requirements for tiny houses ? The Uniform Plumbing Code ( UPC ) and the National Standard Plumbing Code ( NSPC ) address the health and safety provisions for larger houses . Like larger houses , tiny houses must also meet the necessary plumbing requirements found in the codes . However , there are distinct provisions that are particular to only tiny houses ; the 2021 NSPC addresses such provisions in Appendix L .
The 2021 NSPC defines tiny houses as a structure that , when erected , is 400 square feet or smaller . Tiny houses are commonly built on fixed foundations or on wheels . The appropriate local zoning codes will indicate where such tiny houses are permitted . Some may think there are major plumbing design differences for a tiny home , requiring intricate detail , but the plumbing systems are like a standard home . One main difference is that much less material is needed and most tiny house plumbing systems are made up of only one kitchen sink , one lavatory , one shower , and one water closet .
Similarities between tiny houses and larger houses Access to potable water is required for drinking , cleaning and hygiene . Where a fixed potable water supply and meter are available , the water supply and distribution would be installed in accordance with the plumbing code . Sizing the supply and distribution piping will be dictated by the fixtures in the house and the corresponding water supply fixture units ( WSFU ). Where no public water is accessible , alternate methods may be implemented where permitted and regulated by the local jurisdictions . The UPC and NSPC are great resources and contain provisions for alternate water sources such as private water supply systems and storage water tanks .
The drain , waste , and venting piping system will be sized by using the plumbing code tables for Drainage Fixture Units ( DFU ) for all the tiny house fixtures . Just as with a larger home , the drainage is required to be sloped not less than ¼ inch per foot and can deviate where appropriate per the plumbing code . Fixture traps are also required as they are needed to prevent sewer gases from entering the living space .
Water heating for tiny houses is also very similar to a standard plumbing system , only in a smaller capacity . The plumbing code contains water heater sizing provisions based on the first-hour rating method . Water heaters can be a storage tank type or instantaneous type . These water heaters run on natural gas , liquid propane gas , or electricity . The available sources and whether the tiny house will be mobile will dictate the type to consider . Where solar thermal systems are being considered , keep in mind that an auxiliary backup water heater may be required , as weather and storage limitations may not always be reliable in providing hot water .
Determining the location and construction of a tiny home is largely dependent upon how waste disposal from water closets is handled . The option to connect directly to a fixed drainage system where available would be encouraged , as it would allow for self-cleansing water closets that would leave the premise as soon as you flush . However , this is not always an option for more remote or off-the-grid conditions . Composting is a popular alternative and the NSPC contains detailed provisions on the composting system components , materials , design , and maintenance .
Some models are designed to receive drainage from not only a water closet but also lavatories and bathtubs / showers within the same room . These systems liquefy waste and then pump it to the designated drainage system . These systems typically allow the waste to be pumped through a smaller diameter pipe . Such systems contain mechanical pumps and moving parts essential for their functionality . These do work well , but permanent , long term installations may require maintenance .
What about freezing conditions ? Tiny houses built on a lifted frame may contain exposed supply lines , drain-pipes , traps , vents and other piping or tubes subject to freezing . Insulation is the first resort against freezing . You may want to consider sealing and insulating the perimeter of the
www . plumbingafrica . co . za @ plumbingonline @ plumbingonline @ PlumbingAfricaOnline January 2021 Volume 26 I Number 11