How is a manufactured home connected to sewer or septic?

Inside the home, every fixture has a trap and drains into the home's drain piping. The HUD standard says each fixture directly connected to the drainage system "shall be installed with a water seal trap," and that "each manufactured home shall have only one drain outlet."

The outlet has size and clearance rules. It must be at least 3 inches in inside diameter, and it needs a minimum clearance of 3 inches in any direction from parts of the structure, with at least 18 inches of unrestricted clearance directly in front. The drain connector "shall be equipped with a water-tight cap or plug matching the drain outlet," which keeps the opening sealed during transport.

At the site, the installer joins the home's drain to the lot's sewer connection. The installation standard says "the main drain line must be connected to the site's sewer hookup, using an elastomeric coupler or by other methods acceptable to the LAHJ," where LAHJ means the local authority having jurisdiction, such as the local building department. It also says only "qualified personnel familiar with local requirements are permitted to make utility site connections and conduct tests."

### What about slope and testing?

The drain line under the home has to fall toward the outlet. The installation standard says drain lines "must not slope less than one-quarter inch per foot, unless otherwise noted on the schematic diagram," and allows a one-eighth-inch-per-foot slope when a cleanout is installed at the upper end of the run. Slope matters because the standard wants the whole drain system to keep air and waste moving. It says the drainage system "shall be designed to provide an adequate circulation of air in all piping with no danger of siphonage, aspiration, or forcing of trap seals under conditions of ordinary use." A gurgling drain is one sign that air is not moving as it should, and our gurgling drains page explains the causes.

The drainage system "must be inspected and tested for leaks after completion at the site." If a line has been changed or repaired, it should be tested again.

Then the same outlet connects to the septic system's pipe instead of a city sewer, and everything after that point belongs to the septic system. The EPA explains that in a typical septic system, "all water runs out of your house from one main drainage pipe into a septic tank." The tank holds the wastewater long enough for solids to settle, while oil and grease float to the top, and the liquid then goes to a drainfield.

The EPA adds that alternative systems "use pumps or gravity to help septic tank effluent trickle through sand, organic matter (e.g., peat and sawdust), constructed wetlands, or other media," and that some are designed to evaporate or disinfect wastewater before it goes to the soil. Which kind a lot has is something the county records or an inspector can tell you, so do not assume a tank and a drainfield.

Septic systems have their own local rules. In Maricopa County, a person selling or transferring a property served by an onsite wastewater treatment facility "must retain a qualified Inspector to inspect the facility within six months prior to transferring ownership of the property," and the buyer must file a Notice of Transfer within 15 calendar days after the transfer. Our pages on septic tank vs leach field and how often to pump a septic tank cover the system itself.

Whether your home is on sewer or septic is something to confirm before you buy or repair, because the maintenance duties differ between the two. Do not guess from the yard. Ask the park, the seller, the county or a plumber.

Three parts are worth knowing.

• The trap in the floor. The installation standard notes that fittings such as P-traps in the floor are protected with insulation by the manufacturer, and that the insulation must be replaced if removed.
• The connection under the home. The standard requires an access opening at least 18 inches wide and 24 inches high so utility connections under the home can be reached. It also says the main drain line is joined to the site's sewer hookup with "an elastomeric coupler or by other methods acceptable to the LAHJ."
• The pipe sizes. Fixture drains for a single lavatory must be a minimum of 1 1/4 inches, drains serving two or three fixtures a minimum of 1 1/2 inches, and drains for water closets a minimum of 3 inches. The standard also says "no part of the water system shall be connected to any drainage or vent piping."

### Who is responsible for the line?

That depends on where the line is and who owns the lot. In Phoenix, the City says grease and roots are the two primary causes of sewer backups and that property owners are responsible for the sewer line from the house to the connection with the city sewer main. In a park or a rented lot, ask who owns and maintains the line under the lot before you assume it is yours. Our sewer line maintenance page explains how to prevent backups.

### What if the septic system is failing?

The EPA warns that "if the drainfield is overloaded with too much liquid, it can flood." A septic system needs its own care, which our pumping schedule page covers. Maricopa County also states that "a person shall not use a cesspool for sewage disposal," so a cesspool on a lot is something to raise with the county and not something to keep using. If you see wet ground over the drainfield, sewage smell outdoors or slow drains everywhere, call a septic professional.

Check the drain connection the same way you would check a roof or a furnace, before you commit. Ask these questions, and note that each one traces back to a rule above.

• Whether the home is on a sewer or septic system, and who maintains it.
• Whether the drain line has a steady slope, with no sags where water sits.
• Whether the connection under the home has a coupler that is tight and dry.
• Whether the crawlspace has an access opening and whether the lines there are protected. Our frozen lines page covers freeze protection.
• For septic, whether the required inspection was done before the transfer.

Call when you see wet soil under the home, slow drains at several fixtures, sewer smell, or water backing up. Also call before buying a home to have the drain line looked at. The installation standard says the utility connections need qualified personnel, and a plumber can run a camera through the line to check slope and condition.

HQ Plumbing & Air is licensed and insured, gives free estimates and upfront pricing, and answers 24/7.