Rule number one: not into the sanitary sewer
In most municipalities it is illegal to connect a sump pump to the sanitary sewer – the pipe that carries toilet and drain water to the treatment plant. Quakertown Borough in Bucks County, for example, states that sump pump connections to the sanitary sewer are unlawful under borough ordinance, and many Pennsylvania and New Jersey towns have similar rules.
The reason is capacity. Groundwater and stormwater from sump pumps, downspouts and foundation drains (“inflow and infiltration”) can overload sanitary sewers in storms. When that happens, sewage can back up into basements – including yours – and overflow from manholes, as utilities such as Clermont County’s water resources department explain. Some utilities inspect homes for illegal connections or help pay to disconnect them.
Laundry tubs and floor drains are part of the sanitary system too, so running the sump discharge hose into a laundry sink counts as well.
Combined sewer cities (parts of Philadelphia, DC and Chicago) handle stormwater differently; ask your utility what is allowed where you live.
What towns usually allow
New Jersey towns that have adopted sump pump ordinances – such as Verona – and engineering departments like Hillsborough Township’s give similar guidance:
- Preferred: discharge onto your own lawn, mulch, gravel or other absorbent ground so the water soaks in on your property.
- Where that isn’t possible: into a storm sewer, swale, ditch or drainage facility – often only with the town’s approval.
- Not allowed: onto the street or sidewalk (icing hazards in winter), into the sanitary sewer, or toward a neighbor’s property in a way that causes damage or a nuisance.
Rules differ from town to town and sometimes require a permit for a new discharge line. Check with your municipal engineer or code office before you change where the pipe goes.
Don’t let the water come back
- Distance: the discharge should end far enough from the foundation that the water drains away instead of soaking back down to the drain tile and into the pit – a common cause of a sump pump that keeps running.
- Slope: the ground at the outlet should fall away from the house; building codes call for at least 6 inches of fall in the first 10 feet around the foundation (IRC R401.3).
- Splash block or dispersion: spread the water over a lawn or into a pop-up emitter or dry well (where allowed) rather than one concentrated spot.
- Karst areas: in limestone regions such as the Chester Valley or Middle Tennessee, concentrated water can trigger sinkholes – spread it out.
Winter: frozen discharge lines
- Use rigid pipe that slopes continuously so it drains between cycles.
- Avoid long, flat runs of flexible hose on the ground; they hold water and freeze.
- Consider a freeze-protection fitting near the house that lets water escape if the line downstream is blocked by ice.
- Clear snow from the outlet after storms.
Neighbors and shared walls
In rowhomes and twins, discharge options are limited and the water can easily end up next door. Talk to your neighbor before running a line along a shared side, and ask the town about routing to the street drain or a storm connection where permitted.
Questions to ask your contractor
- Where will the discharge go, and is that allowed by our town?
- How will you keep the line from freezing?
- Will the water drain away from the foundation and away from neighbors?
- Is a permit needed for the discharge line or a storm sewer connection?
Sources
- Quakertown Borough (Bucks County, PA): Sump pump connections
- Hillsborough Township (Somerset County, NJ): Sump pump discharge reminder
- Township of Verona, NJ: Ordinance creating sump pump regulations (2022)
- Clermont County (Ohio) Water Resources: Inflow and infiltration FAQ
- International Residential Code R401.3 (drainage), as proposed/published by the ICC