How to Inspect Mobile Homes or Manufactured Housing for Plumbing System Defects:
Detailed mobile home, trailer or doublewide plumbing inspection procedures, defect lists, references to plumbing standards for mobile homes, trailers, double-wide home plumbing water supply & drain piping and oil or gas fuel piping.
Mobile home septic systems are also addressed.
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Ver.4.0 - 04/25/07, updated through January 2018 - Steve Vermilye, New Paltz NY and Daniel Friedman, Poughkeepsie NY, Hudson Valley ASHI Chapter Seminar, Newburgh NY, January 4, 2000, NY Metro ASHI Fall 99 Seminar, Holiday Inn Crowne Plaza, White Plains NY, October 2, 1999. Our page top photo shows our associated Steve Vermilye inspecting an on-ground, tipping, heating oil tank at a mobile home occupied by farm workers in Ulster County, N.Y.
Our photo (below-left) illustrates an area of plumbing drain leaks below the sink in a doublewide home - rot destroyed the subfloor, invited carpenter ants into the structure, and soaked insulation.
Heat Tapes - use metal-braid shielded type connected to GFCI so if a short will trip. Heat tapes, especially the non-shielded types, short and start fires, especially if crossed over themselves or otherwise improperly installed.
PART 3280—MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS [PDF] Complete text of 24 CFR Part 3280 - MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS contains 10 subparts pertaining to General (data plate and certification contents and locations), Plans (dimensions, exits, etc), Fire Safety, Body and Frame, Testing, Thermal Protection, Heating/Cooling and venting systems, Electrical, and Transportation (axles, springs, drawbar). It's about 90 pages of regulations.
(a) Minimum requirements. Any plumbing system installed in a manufactured home shall conform, at least, with the provisions of this subpart.
(1) General. The plumbing system shall be of durable material, free from defective workmanship, and so designed
and constructed as to give satisfactory service for a reasonable life expectancy.
(2) Conservation. Each water closet must not use more than 1.6 gallons of water per flush.
(3) Connection to drainage system. All plumbing, fixtures, drains, appurtenances, and appliances designed or used to receive or discharge liquid waste or sewage shall be connected to the manufactured home drainage system in a manner provided by this standard.
(4) Workmanship. All design, construction, and workmanship shall be in conformance with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this standard.
(5) Components. Plumbing materials, devices, fixtures, fittings, equipment, appliances, appurtenance, and
accessories intended for use in or attached to a manufactured home shall conform to one of the applicable standards
referenced in §3280.604. Where an applicable standard is not referenced, or an alternative recognized standard is utilized, the plumbing component shall be listed by a nationally recognized testing laboratory, inspection agency or other qualified organization as suitable for the intended use.
(6) Prohibited fittings and practices. (i) Drainage or vent piping shall not be drilled and tapped for the purpose of
(ii) Except as specifically provided elsewhere in this standard, vent pipes shall not be used as waste or drain pipes.
(iii) Fittings, connections, devices, or methods of installation that obstruct or retard the flow of sewage, or air in the
drainage or venting systems in an amount greater than the normal frictional resistance to flow shall not be used unless
their use is acceptable in this standard or their use is accepted as having a desirable and acceptable function of ultimate
benefit to the proper and continued functioning of the plumbing system.
(iv) Cracks, holes, or other imperfections in materials shall not be concealed by welding, brazing, or soldering or by
paint, wax, tar, or other leaksealing or repairing agents.
(v) Piping, fixtures or equipment shall be located so as not to interfere with the normal use or with the normal
operation and use of windows, doors or other required facilities.
(vi) Galvanized pipe shall not be bent or welded.
(7) Alignment of fittings. All valves, pipes, and fittings shall be installed in correct relationship to the direction of flow.
(b) Protective requirements.
(1) Cutting structural members. Structural members shall not be unnecessarily or
carelessly weakened by cutting or notching.
(2) Exposed piping. All piping, pipe threads, hangers, and support exposed to the weather, water, mud, and road
hazard, and subject to damage therefrom, shall be painted, coated, wrapped, or otherwise protected from deterioration.
(3) Road damage. Pipes, supports, drains, outlets, or drain hoses shall not extend or protrude in a manner where they
could be unduly subjected to damage during transit.
(4) Freezing. All piping and fixtures subject to freezing temperatures shall be insulated or protected to prevent
freezing, under normal occupancy. The manufacturer shall provide:
(i) Written installation instructions for the method(s) required for compliance to this section;
(ii) A statement in the installation instructions required by §3280.306(b), stating that if the heat tape or pipe heating cable is used, it must be listed for use with manufactured homes.
(iii) A receptacle outlet complying with §3280.806(d)(10).
(5) All piping, except the fixture trap, shall be designed to allow drainage.
(6) Rodent resistance. All exterior openings around piping and equipment shall be sealed to resist the entrance of
(7) Piping and electrical wiring shall not pass through the same holes in walls, floors or roofs. Plastic piping shall not be exposed to heat in excess of manufacturers recommendation or radiation from heat producing appliances.
[40 FR 58752, Dec. 18, 1975, as amended at 42 FR 54383, Oct. 5, 1977. Redesignated at 44 FR 20679, Apr. 6, 1979, as amended
at 58 FR 55012, Oct. 25, 1993; 78 FR 73985, Dec. 9, 2013]
(a) Tightness. Joints and connections in the plumbing system shall be gastight and watertight for the pressures required under testing procedures.
(b) Assembling of pipe. All joints and connections shall be correctly assembled for tightness. Pipe threads shall be
fully engaged with the threads of the fitting. Plastic pipe and copper tubing shall be inserted to the full depth of the solder
cup or welding sockets of each fitting. Pipe threads and slip joints shall not be wrapped with string, paper, putty, or similar
(c) Threaded joints. Threads for screw pipe and fittings shall conform to the approved or listed standard. Pipe ends
shall be reamed out to size of bore. All burrs, chips, cutting oil and foreign matter shall be removed. Pipe joint cement or
thread lubricant shall be of approved type and applied to male threads only.
(d) Solder joints. Solder joints for tubing shall be made with approved or listed solder type fittings. Surfaces to be
soldered shall be cleaned bright. The joints shall be properly fluxed with noncorrosive paste type flux and, for
manufactured homes to be connected to a public water system, made with solder having not more than 0.2 percent lead.
(e) Plastic pipe, fittings and joints. Plastic pipe and fittings shall be joined by installation methods recommended by
the manufacturer or in accordance with the provisions of a recognized, approved, or listed standard.
(f) Union joints. Metal unions in water piping shall have metaltometal ground seats.
(g) Flared joints. Flared joints for softcopper water tubing shall be made with approved or listed fittings. The tubing
shall be expanded with a proper flaring tool.
(h) Cast iron soil pipe joints. Approved or listed cast iron pipe may be joined as follows:
(1) Approved or listed hubless pipe and fittings must be permitted to be joined with listed couplings or adapters, per
the manufacturer's recommendations.
(2) Hub and plainend soil pipe may be joined by compression fittings per the manufacturer's recommendation
(1) Traps required. Each plumbing fixture, except listed toilets, shall be separately trapped by approved water seal “P” traps. All traps shall be effectively vented.
(2) Combination Fixtures. For the purposes of drainage and ventilation requirements, a two or threecompartment
sink, up to three single sinks, or up to three lavatories may be connected to one “P” trap and considered as a single
fixture, so long as the sinks and lavatories are in the same room, have waste outlets not more than 30 inches apart, and
have flood level rims at the same level. The “P” trap must be installed at the center fixture when three such fixtures are
(3) Prohibited traps. A trap which depends for its seal upon concealed interior partitions shall not be used. Full “S”
traps, bell traps, drum traps, crownvented traps, and running traps are prohibited. Fixtures shall not be doubletrapped.
(4) Material and design. Each trap shall be selfcleaning with a smooth and uniform interior waterway. Traps shall be
manufactured of cast iron, cast brass, or drawn brass tubing of not less than No. 20 Brown and Sharpe gage, or approved
or listed plastic, or other approved or listed material. Union joints for a trap shall be beaded to provide a shoulder for the
union nut. Each trap shall have the manufacturer's name stamped or cast in the body of the trap, and each tubing trap
shall show the gage of the tubing.
(5) Trap seal. Each “P” trap shall have a water seal of not less than 2 inches and not more than 4 inches and shall be
set true to its seal.
(6) Size. Traps shall be not less than 1
inches in diameter. A trap shall not be larger than the waste pipe to which it
(7) Location. Each trap shall be located as close to its vent and to its fixture outlet as structural conditions will permit.
(8) Length of tailpiece. The vertical distance from a trap to the fixture outlet shall not exceed 24 inches.
(9) Installation. (i) Grade of trap arm. The piping between a “P” trap and the fixture tee or the vented waste line shall
inch per foot towards the vent and in no event shall have a slope greater than its diameter. The vent opening
at fixture tees shall not be below the weir of the “P” trap outlet.
(ii) Trap arm offset. The piping between the “P” trap and vent may change direction or be offset horizontally with the
equivalent of no more than 180 degrees total change in direction with a maximum of 90 degrees by any one fitting.
(iii) Concealed traps. Traps with mechanical joints shall be accessible for repair and inspection.
(iv) Removability of traps, etc. Traps shall be designed and installed so the “U” bend is removable without removing
the strainers from the fixture. Continuous waste and tail pieces which are permanently attached to the “U” bend shall also
be removable without removing the strainer from the fixture.
(b) Cleanout openings—(1) Location of cleanout fittings. (i) Cleanouts shall be installed if the drainage system cannot be cleaned through fixtures, drains, or vents. Cleanouts shall also be provided when fittings of more than 45 degrees are used to affect an offset except where long turn ells are used which provide sufficient “sweep” for cleaning.
(ii) A full size cleanout shall be installed at the upper end of any section of drain piping which does not have the
required minimum slope of
inch per foot grade.
(iii) A cleaning tool shall not be required to pass through more than 360 degrees of fittings, excluding removable “P”
traps, to reach any part of the drainage system. Water closets may be removed for drainage system access.
(2) Access to cleanouts. Cleanouts shall be accessible through an unobstructed minimum clearance of 12 inches
directly in front of the opening. Each cleanout fitting shall open in a direction opposite to the flow or at right angles to the
pipe. Concealed cleanouts that are not provided with access covers shall be extended to a point above the floor or outside
of the manufactured home, with pipe and fittings installed, as required, for drainage piping without sags and pockets.
(3) Material. Plugs and caps shall be brass or approved or listed plastic, with screw pipe threads.
(4) Design. Cleanout plugs shall have raised heads except that plugs at floor level shall have countersunk s...
(a) General requirements—(1) Quality of fixtures. Plumbing fixtures shall have smooth impervious surfaces, be free
from defects and concealed fouling surfaces, be capable of resisting road shock and vibration, and shall conform in quality
and design to listed standards. Fixtures shall be permanently marked with the manufacturer's name or trademark.
(2) Strainers. The waste outlet of all plumbing fixtures, other than toilets, shall be equipped with a drain fitting that will
provide an adequate unobstructed waterway.
(3) Fixture Connections. Fixture tailpieces and continuous wastes in exposed or accessible locations must be of not
less than No. 20 Brown and Sharpe gauge seamless drawnbrass tubing or other approved pipe or tubing materials.
Inaccessible fixture connections must be constructed according to the requirements for drainage piping. The diameter of
each fixture tailpiece, continuous waste, or waste and overflow must be not less than:
inches, for sinks of two or more compartments, dishwashers, clothes washing machines, laundry tubs,
bathtubs, and showers; and
(ii) Not less than 1
inches for lavatories or single compartment sinks having a 2inch maximum drain opening.
(4) Concealed connections. Concealed slip joint connections shall be provided with adequately sized unobstructed
access panels and shall be accessible for inspection and repair.
(5) Directional fitting. An approved or listed “Y” or other directionaltype branch fitting shall be installed in every
tailpiece or continuous waste that receives the discharge from food waste disposal units, dishwashing, or other forcedischarge
fixture or appliance. (See also §3280.607(b)(4)(ii).)
(6) Water conservation. All lavatory faucets, showerheads, and sink faucets must not exceed a flow of 2.5 gallons per
(1) Spacing. All plumbing fixtures shall be so installed with regard to spacing as to be reasonably accessible for their intended use.
(2) Water closets.
(i) Water closets shall be designed and manufactured according to approved or listed standards
and shall be equipped with a water flushing device capable of adequately flushing and cleaning the bowl at each operation
of the flushing mechanism.
(ii) Water closet flushing devices shall be designed to replace the water seal in the bowl after each operation. Flush
valves, flushometer valves, flushometer tanks and ballcocks shall operate automatically to shut off at the end of each flush
or when the tank is filled to operating capacity.
(iii) All water closets must be low consumption (1.6 gallons per flush (gpf)) closets.
(iv) Flush tanks shall be fitted with an overflow pipe large enough to prevent flooding at the maximum flow rate of the
ball cock. Overflow pipes shall discharge into the toilet, through the tank.
(v) Floor Connection. Water closets must be securely bolted to an approved flange or other approved fitting that is secured to the floor by means of corrosionresistant screws.
The bolts must be of solid brass or other corrosionresistant
material and must not be less than
inch in diameter. A watertight seal must be made between the water closet and
flange or other approved fitting by use of a gasket, sealing compound, or listed connector device.
(vi) Floor connection. Water closets shall be securely bolted to an approved flange or other approved fitting which is
secured to the floor by means of corrosionresistant screws. The bolts shall be of solid brass or other corrosionre... material and shall be not less than onefourth inch in diameter. A watertight seal shall be made between the water closet
and flange or other approved fitting by use of a gasket or sealing compound.
(3) Shower compartment. (i) Each compartment stall shall be provided with an approved watertight receptor with sides and back extending at least 1 inch above the finished dam or threshold. In no case shall the depth of a shower receptor be less than 2 inches or more than 9 inches measured from the top of the finished dam or threshold to the top of the drain.
The wall area shall be constructed of smooth, noncorrosive, and nonabsorbent waterproof materials to a height not less
than 6 feet above the bathroom floor level. Such walls shall form a watertight joint with each other and with the bathtub,
receptor or shower floor. The floor of the compartment shall slope uniformly to the drain at not less than onefourth nor
more than onehalf inch per foot.
(ii) The joint around the drain connection shall be made watertight by a flange, clamping ring, or other approved listed
(iii) Shower doors and tub and shower enclosures shall be constructed so as to be waterproof and, if glazed, glazing
shall comply with the Standard for Safety Glazing Materials used in Buildings—Safety Performance Specifications and
Methods of Test, ANSI Z97.12004 (incorporated by reference, see §3280.4).
(iv) Prefabricated plumbing fixtures shall be approved or listed.
(v) Shower and tubshower combination valves must be balanced pressure, thermostatic, or combination mixing valves that conform to the requirements of ASSE 10162005, Performance Requirements for Automatic Compensating Valves for Individual Shower and Tub/Shower Combinations (incorporated by reference, see §3280.4).
Such valves must
be equipped with handle position stops that are adjustable in accordance with the valve manufacturer's instructions and to
a maximum setting of 120 °F. Hot water supplied to bathtubs and whirlpool bathtubs are to be limited to a temperature of
not greater than 120 °F by a water temperature limiting device that conforms to the requirements of ASSE 10702004,
Performance Requirements for Water Temperature Limiting Devices (incorporated by reference, see §3280.4).
(4) Dishwashing machines. (i) A dishwashing machine must discharge its waste through a fixed air gap installed above the machine, through a high loop as specified by the dishwashing machine manufacturer, or into an open standpipe receptor with a height greater than the washing compartment of the machine. When a standpipe is used, it must be at least 18 inches, but not more than 30 inches, above the trap weir. The drain connections from the air gap or high loop are permitted to connect to an individual trap to a directional fitting installed in the sink tailpiece or to an opening provided on the inlet side of a food waste disposal unit.
(ii) Drain from a dishwashing machine shall not be connected to a sink tailpiece, continuous waste line, or trap on the
discharge side of a food waste disposal unit.
(5) Clothes washing machines. (i) Clothes washing machines shall drain either into a properly vented trap, into a
laundry tub tailpiece with watertight connections, into an open standpipe receptor, or over the rim of a laundry tub.
(ii) Standpipes must be either 1 1 ∕2 inch diameter minimum nominal iron pipe size, 1 1 ∕2 inch diameter nominal brass tubing of not less than No. 20 Brown and Sharp gauge, or 1 1∕2 inch diameter approved plastic materials.
discharge into a vented trap or must be connected to a laundry tub appliance by means of an approved or listed directional
fitting. Each standpipe must extend not less than 18 inches or more than 42 inches above its trap and must terminate in an
accessible location no lower than the top of the clothes washing machine. A removable, tightfitting cap or plug must be
installed on the standpipe when the clothes washer is not provided.
(iii) Clothes washing machine drain shall not be connected to the tailpiece, continuous waste, or trap of any sink or
(1) Access. Each plumbing fixture and standpipe receptor shall be located and installed in a manner
to be accessible for usage, cleaning, repair and replacement. Access to diverter valves and other connections from the
fixture hardware is not required.
(2) Alignment. Fixtures shall be set level and in true alignment with adjacent walls. Where practical, piping from fixtures shall extend to nearest wall.
(3) Brackets. Wallhung fixtures shall be rigidly attached to walls by metal brackets or supports without any strain
being transmitted to the piping connections. Flush tanks shall be securely fastened to toilets or to the wall with corrosiveresistant
(4) Tub supports. Bathtub rims at wall shall be supported on metal hangers or on endgrain wood blocking attached to
the wall unless otherwise recommended by the manufacturer of the tub.
(5) Fixture fittings. Faucets and diverters shall be installed so that the flow of hot water from the fittings corresponds to
the lefthand side of the fitting.
(6) Hydromassage bathtub—(i) Access panel. A door or panel of sufficient size must be installed to provide access to
the pump for repair or replacement.
(ii) Piping drainage. The circulation pump must be accessibly located above the crown weir of the trap. The pump
drain line must be properly sloped to drain the volute after fixture use.
(iii) Piping. Hydromassage bathtub circulation piping must be installed to be selfdraining.
(iv) Electrical. Wiring must comply with Articles 680.70, 680.71, and 680.72 of the National Electrical Code, NFPA No. 702005.
See the full text in PART 3280—MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS [PDF] newer copy retrieved 2017/07/13 - faster-loading
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Question: (Dec 29, 2011) kenneth said:
how do i hook water to a mobile home that i set up on my farm from the well and the deep pump that i already have supplying water to the farm house can i just T into that line with a check valve and run the line to the mobile home were i have put another presure tank and wire the low presure switch to the pump on a switch at the pump so that if the farm house calls for water at the same time that it will just trip the breaker instead of over loading the pump with electricty
Kenneth if the mobile home is close to the main building, you can run a water supply line teed off of the in-building cold water supply line in the main building right over to the mobile home. If you live in an area of freezing weather, however, you'll need to worry about burying the line to protect from frost.
For greater distances, say 100feet or more, you may want to install a second pressure tank and booster pump to deliver decent pressure and flow at the second home.
(Aug 16, 2012) Michael said:
does a pressure tank underneath a double wide with vinyl skirting need to be insulated.
would building a 'box' around it with rigid styrofoam insulation be agood idea?
why dont they just put the pressure tank inside the heated space
In prolonged cold weather even an insulated box won't prevent freezing pipes or a frozen water tank, but if you insulate the skirt (and possibly the ground surface) and add even a small heat source that may work find.
(Jan 11, 2013) dar said:
Hello my question is what kind of plumbing vent is commonly used on "manufactued homes"?
Currently manufactured homes usually use plastic or PVC piping for plumbing vents but copper may still be found at some installatins.
(Feb 6, 2013) dena said:
we are having trouble with the drainage from the kitchen sink
on a 1999 redman double wide mobile home underneath all is covered with plastic
does it have a clean out plug on the ends of the plumbing? i sure don't want to tear out
all the plastic put a 30 foot down the drain and didn't find nothin
Dena take a look at BLOCKED DRAIN REPAIR METHODS and let me know if questions remain.
(Mar 28, 2014) janis said:
I can still hear water running after the main shut off water valve to the mobil home has been turned off. Why? Is there another location for another valve? There isn't any water coming from the taps but the hot water tank seems to want to continue to fill.
On some mobile homes the water heater may be fed by a separate feeder line beneath the home and "ahead" of what you think is the main water shutoff. Take a look inside the water heater closet and also look beneath the home. Follow the water supply pipe from where it is first visible.
Let us know what you find.
(May 4, 2014) Anonymous said:
where is the location of hot water heater in a1998 summit moble home
Anon, I can't cite a specific always-location, but if you don't see the water heater accessible from inside, often you'll find a door in the mobile home's exterior wall - from outdoors - that opens to give access to the heater.
If your heater uses gas or oil, walk away from the home far enough to see its roof - look for the chimney or vent as that will typically be right over the water heater.
If your water heater is electric you can find it by following the electrical wire circuit for that appliance.
(July 1, 2014) Angie said:
We have really hard water our cold water either has no pressure or the lines are blocked how can you check?
Angie, start by checking the pressure gauge right at the pressure tank or water meter.
Then see WATER SOFTENERS & CONDITIONERS
(Aug 10, 2014) Anonymous said:
I had a plumber come out this morning, I had a leak under my mobile home. He did not have the part to fix it and said he could cap off the main bathroom, so I would have water to the rest of the house. He capped it and now I only have hot water and he can't figure out why. He said something about a T, but can't find where it would hook into. This is a big name company. Any help out there?
Your plumber might have to go to the trouble of crawling into the space below the home (get him some knee pads and maybe he'll get to work). There he may need to move insulation aside or temporarily remove a rat-screen to get access to and follow the piping to find where repairs are needed.
(Nov 28, 2014) Debra said:
I have a 2007 clayton s/w mobile that was only occupied for one year. After that the water was turned off and it has been sitting for close to 3 years. Just wondering if this would be harmful to the water connections,since there was no heat in the mobile during the winter months.
If the plumbing was not drained and if you were in a freezing climate you'd want to look out for leaks.
Beyond that, flush out or have a plumber sanitize the
water supply piping.
(Nov 28, 2014) Debra said:
I had drained all the water lines before the winter as soon as the water was cutoff. The only reason I asked about damage to the plumbing was because under the kitchen sink, both of the plastic nuts that hold the pex lines up to the fixture were cracked. I replaced them,and checked the ones under the bathroom sink,which were not damaged.Since,it is so difficult to get to all the supply lines I was unable to check any further.
In cases such as the one you describe, people might try turning on the water but be sure to check everywhere, starting below the unit, immediately to see if there is leakage.
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