Sort the cause in four checks
- 1
Check the weather
Water that appears only after heavy rain or snowmelt usually comes from outside. Water that appears on a dry week points to a pipe or fixture.
- 2
Read the water meter
Turn off every fixture and appliance, then watch the meter dial or low-flow indicator. If it moves, you have a leak somewhere on the property.
- 3
Look at the location
Wet along a wall base after rain is exterior. Wet near a floor drain, laundry, water heater or stack is more often plumbing.
- 4
Smell and taste the clue
A sewage smell or gray, dirty water points to a drain backup. Clear water with no smell may be groundwater or a supply leak.
If the meter moves with everything off, treat it as a plumbing leak first. A supply line leak can run for weeks inside a wall or slab before it shows.
Who fixes what
| Where the water starts | Typical clue | Fix type |
|---|---|---|
| Supply pipe or fitting | Meter moves, damp wall or ceiling, hissing | Plumbing, start with leak detection |
| Water heater or washer hose | Pooling near the appliance, rust or stains | Plumbing |
| Floor drain backing up | Gray water, smell, gurgling | Plumbing, drain or sewer work |
| Failed or missing sump pump | Pit overflows after rain | Plumbing, see sump pump service |
| Cracked foundation wall | Seepage at wall base after rain | Foundation or waterproofing contractor |
| Poor grading or gutters | Water pools by the house outside | Landscaping and gutter work |
| High water table | Rising water through the floor slab | Drainage system or waterproofing contractor |
A general guide. Some basements have more than one cause at once.
Mixed cases are common. A sump pit that works fine can still overflow if the drain tile is clogged, and a foundation crack can sit next to a pinhole leak in a copper line.
Plumbing causes people miss
Pinhole leaks in copper, a failed washer hose, a weeping water heater fitting and a leaking toilet supply are the quiet ones. They drip for days and often get blamed on rain. Check the walls near the pipes, the ceiling below bathrooms and the base of the water heater.
Sewer and drain causes are louder. A clogged main line pushes water up through the lowest drain, often a basement floor drain or laundry tub. If you see backup after heavy rain, the cause may be the lateral, the public main, or a combination. A camera run through your line can show which part is failing, and a sump pump that works can still be overwhelmed when the ground is saturated.
Water on the basement floor?
Tell us what you see and when it started. We will tell you if it sounds like plumbing and what to do while you wait.
Melrose note: the sewer program and your basement
Melrose began working on infiltration and inflow in 2016 with a citywide flow metering program using 30 meters for 10 weeks.
Infiltration is groundwater leaking into sewer pipes, and inflow is stormwater entering through connections. The city reports 74 miles of sewer mains, about 57 percent of them and 500 manholes inspected by camera. It also reports over 50,000 linear feet of lining and 19 manholes rehabilitated. More than $9 million has gone into this work, funded through an MWRA grant and loan program.
What it means for you: the public main may be improving, but the city's work is on the public mains, so a problem inside your house or on the pipe serving it still needs its own check. The city's code includes sections titled Separating surface water from wastewater, Infiltration and inflow mitigation fees, and Discharge of clean water to sanitary sewers. Ask the city how these apply to your sump or downspouts before you connect anything to the sewer.
The city also ran citywide water main flushing in 2025, from September 8 into late October. Flushing can cloud the water or knock sediment loose. If you find actual water inside, check your own pipes. If you see actual water inside after flushing, check your own pipes.
Source type: City of Melrose Water and Sewer Projects page, Melrose Code index, City flushing notice
What we do and what we do not
Honest scope saves you money. Here is how we split it.
We handle (plumbing)
- Leak detection and repair on supply and drain lines
- Sump pump installation, repair and replacement
- Floor drain, drain line and sewer backup problems
- Water heater, washer and fixture leaks
Another contractor handles (exterior water)
- Foundation wall cracks and sealing
- Grading, gutters and downspout routing outside
- Perimeter drain systems and interior waterproofing
- Slab-level water table issues
If your basement has both, we will fix the plumbing and point you to the right contractor for the rest.
While you wait for help
- Stop the source if you canShut off the water at the main if a supply leak is running.
- Cut power near waterDo not walk through standing water near outlets or an energized panel.
- Move valuables upLift boxes, rugs and electronics off the floor.
- Photograph everythingTake dated photos of the water, the source and any damage for insurance.
- Do not run drainsIf the cause might be a backup, hold off on sinks, showers and laundry.
Keep it simple until the cause is known. We also serve Stoneham and Wakefield.
Sewage in the basement is a health issue
Backed-up sewage carries bacteria. Keep kids and pets out, wear gloves and boots if you must enter, and wash well afterward. Porous items that touched sewage usually cannot be saved.
If water is rising near the electrical panel or you smell gas, leave the building and call 911 or the gas utility from outside.
Questions we hear
The city code has sections titled Separating surface water from wastewater and Discharge of clean water to sanitary sewers. Ask the city before you connect a discharge to the sewer.
Not always. A sump pump helps where groundwater collects in a pit. If the water comes from a leaking pipe, a pump will not fix it.
Check the meter with all water off. If it moves, it is a plumbing leak. If water shows up only after rain, it is likely from outside.
Flushing may cloud water or loosen sediment. If you find water on the floor during or after flushing, check your own pipes and the shutoff. If you find water on the floor during or after flushing, check your own pipes.
It depends on the policy and the cause. Sudden pipe bursts are often covered, while groundwater seepage and sewer backups often need an added endorsement. Ask your insurer and keep photos.
No. We do plumbing work: leaks, drains, sewer lines and sump pumps. If your problem is foundation seepage or grading, we will say so and suggest the right type of contractor.