Drain and sewer glossary

Backwater valve · Belly · Cable machine (snake / auger) · Camera inspection (sewer scope) · Cast iron · Catch basin · Cleanout · Clay tile · Combined sewer · Cured-in-place pipe (CIPP / lining) · FOG (fats, oils, grease) · Footage mark · French drain · Grease trap / interceptor · Hydro jetting · Infiltration · Lateral · Locate (sonde locate) · Main line · Orangeburg · Pipe bursting · P-trap / trap seal · Root intrusion · Sanitary sewer · Scale (tuberculation) · Spot repair · Standpipe · Storm drain · Sump pump · Vent stack

Backwater valve

A one-way valve on a basement fixture or lateral that lets wastewater out but slams shut against incoming sewer surges. PWD installs them free for qualifying homes through the Basement Backup Protection Program.

Belly

A low sag in a lateral where solids settle. The one defect trenchless lining cannot fix, because lining preserves the existing slope — bellies need excavation or regrading.

Cable machine (snake / auger)

A rotating steel cable that bores through obstructions. Opens flow but leaves wall coatings behind — the reason repeat clogs keep a schedule.

Camera inspection (sewer scope)

A waterproof camera pushed through the line, recording defects with footage marks. The only honest basis for pricing sewer repair; you keep the video.

Cast iron

Drain and stack pipe standard in pre-1975 homes. Corrodes from the invert outward into rough scale that catches everything — the classic repeat-clog pipe.

Catch basin

The grated inlet that takes street and lot runoff into the storm system. Leaves pack them every October; a flooded corner is usually a packed grate, not a broken pipe.

Cleanout

The capped access riser that gives tools a straight shot into the line. No cleanout means pulling a toilet or going through the roof vent — slower and costlier.

Clay tile

Segmented vitrified-clay pipe in pre-1940 laterals with mortared joints. Sound for a century until roots find the joints — then it becomes a root farm.

Combined sewer

One pipe carrying sewage and stormwater, standard in older Philadelphia. Violent storms surcharge it and push flow back toward basements — the mechanism behind most city backups.

Cured-in-place pipe (CIPP / lining)

A resin-saturated liner inverted into the old pipe and cured into a pipe-within-a-pipe. Needs a jetted-clean host pipe and correct slope; cannot fix bellies or collapses.

FOG (fats, oils, grease)

Kitchen waste that congeals in cool joints and narrows the bore. The number-one cause of restaurant line failures and November residential surges.

Footage mark

The distance reading on camera footage locating each defect from the access point — what lets a second contractor bid from your video without re-scoping.

French drain

A gravel trench with perforated pipe that collects groundwater. Distinct from foundation drains; when its outlet silts shut, the yard goes swampy.

Grease trap / interceptor

The box (inside) or tank (outside) that strips FOG before wastewater reaches the sewer. Pump-out intervals run by volume; neglected traps feed the main line.

Hydro jetting

High-pressure water — typically 1,500 to 4,000 PSI — scours the full pipe wall through rear-facing jets. Cleaning, not just clearing; camera clearance first on old pipe.

Infiltration

Groundwater entering through cracked joints and defects. Consumes pipe capacity and carries silt that settles into bellies — worst in February thaw and saturated August soil.

Lateral

The pipe from the building to the public main, including the stretch under the street. In most Philadelphia-area jurisdictions it is the owner’s responsibility end to end.

Locate (sonde locate)

A transmitter on the camera head tracked from the surface, marking each defect’s position and depth for excavation or competing bids.

Main line

The building’s primary drain run to the lateral, or the public main in the street. Whole-house symptoms mean the problem is here, not at a fixture.

Orangeburg

Tar-impregnated wood-fibre pipe installed roughly 1945–1972. Rated 30–50 years, now all past it: softens, deforms, collapses. Generally cannot be jetted or lined.

Pipe bursting

A bursting head pulls new pipe through the old line’s path, fracturing the host outward. Replaces without lining’s slope limits but needs launch and receive pits.

P-trap / trap seal

The water bend blocking sewer gas. Floor drains in dry basements evaporate their seals — the commonest cause of basement sewage smells, fixed with a bucket of water.

Root intrusion

Fine roots entering through joints and growing into mats. Cutting clears them; only repairing the joint stops their return. London planes and silver maples are the usual offenders.

Sanitary sewer

The pipe carrying wastewater only — distinct from storm and combined systems. Storm water in it (or sewage in storm pipe) is a prohibited cross-connection.

Scale (tuberculation)

Mineral and corrosion crust inside cast iron that narrows the bore. Chain-flail descaling removes it only while wall thickness remains — scale sometimes is the wall.

Spot repair

Excavating and replacing one failed section rather than the whole run. Resolves most localized defects at a fraction of full replacement.

Standpipe

A vertical extension on a floor drain that raises the overflow point — cheap backup-height insurance while waiting for a valve.

Storm drain

Any pipe or inlet carrying rainwater only. In combined-sewer districts much of it shares pipe with sewage, which is why storms back up basements.

Sump pump

The pit pump keeping groundwater below slab level. Test with a bucket each March; confirm the discharge outlet stays clear of ice and snow.

Vent stack

The roof-terminated pipe admitting air so drains flow and traps hold. A blocked vent gurgles and siphons traps dry — mimicking a clog with no blockage at all.