Common Plumbing Design Mistakes 21-30
Click on an item below to view additional information and suggestions on how to avoid the mistake .

 21.  Improperly sized floor drain for water softener backwash.
            a) Verify flow rate of equipment discharge.
            b) Size floor drain and piping to prevent splashing and flooding.
 22.  Neglecting to specify valve stem extensions.
            a) Specify extensions for valves installed in insulated lines.
 23.  Lack of information on drawings or specifications requiring water hammer arrestors.
            a) Include requirement on drawings and/or specifications for shock absorbers at all quick-closing valves and faucets.
            b) Indicate shock absorber size on drawings at each occurence.
 24.  No provisions on drawings for equipment housekeeping pads.
            a) Note and size reinforced concrete housekeeping pads for major equipment.
            b) Specify epoxy coating on concrete pads beneath water softener brine tanks.
 25.  Failure to provide traps and vents on open storm drains within a building.
            a) Floor drains within a building which are connected to a storm drainage system must have traps and vents
                 to prevent possible entrance of odors.
            b) Size and design traps and vents same as for sanitary systems.
            c) Do not connect storm vents into sanitary venting.
 26.  Omission of natural gas pressure regulator venting.
            a) Provide gas pressure regulator relief vents on all regulators located within a building where gas inlet pressure is 1 psi or greater.
            b) Indicate on drawings; routing, size and termination of relief vents.
 27.  Specifying plastic drainage piping beneath multi-story buildings.
            a) Specify cast iron drainage piping for buildings over three stories in height.
 28.  Not specifying grout between fixture and walls/floors.
            a) Include requirement on drawings or within specifications for providing grout where fixtures meet walls
                 and/or floors.
 29.  Unclear or no calculations within design file for various systems.
            a) Produce complete design calculations for all plumbing systems and equipment included with the project.
            b) Include all calculations within a design file.
            c) All calculations should be prepared in an orderly manner to allow others to easily follow the design process.
 30.  Failing to provide pipe coating specifications for piping susceptible to corrosion.
            a) Require proper coating protection for all steel and copper piping buried below ground.
            b) Determine corrosiveness of soil and require proper coating for buried cast iron and ductile iron
                 piping where required.
            c) Specify proper coating on piping located above ground in corrosive atmospheres.
                 (i.e. - Enclosed swimming pools, chemical processing areas, etc.).
            d) Require proper coating protection for all bare steel piping located outside above ground, including
                 piping on roof.