Welcome to D.O. Smith, we are a product design and development workshop located in Los Angeles California. We have been in business since the first design and development of the first double test plug for plumbers which was made in 1939. Since then we have grown and expanded our services to include Computer numerical controlled product development (CNC), and have also built a factory to be able to create molds to work with metal materials which include Aluminium, Brass, and Cast-Iron. With both our CNC and foundry manufacturing we can design almost any product from the beginning stages to final product development.

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Plumbing Distributers / Suppliers

D.O. Smith protects all its partners by only selling to distributors. We do not sell to retail customers directly. We refer all calls to local suppliers within their area. Help us support honest business practices.


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Plumbers double test plugs.

American Made

Quality product design and development.