Basement Flooding and Sewer Backup Cleanup in Manchester NH

Basement flooding and sewer backup cleanup

Manchester basements take water three ways: groundwater and snowmelt through the floor and walls, a sump pump that fails, and sewage backing up through the floor drain. Each is cleaned differently and insured differently. Sewage is black water, which Fixr prices at $7 to $7.50 per square foot, about double clean water.

Updated October 29, 2026

Which water is it?

Where it came from	What cleanup involves	Usual insurance
Burst pipe, water heater, washer	Clean water: extract and dry	Homeowners, if sudden
Groundwater or snowmelt through walls or floor	Extract and dry; find the entry point	Often excluded; flood policy only if it is a flood
River or surface flooding	Contaminated: remove porous materials, sanitize	Flood policy (NFIP or private)
Sewer backup through a floor drain	Black water: remove porous materials, sanitize	Only with a sewer backup endorsement

Combined sewers

In much of Manchester the same pipes carry rainwater from the streets and sewage from buildings. The city says the overflows to the Merrimack are there to keep that mixture from backing up into streets and basements in heavy rain. A backflow prevention device on the sewer line is the usual defense. The city's CSO 50/50 Sewer Backflow Program reimburses part of an approved device for properties entirely inside the combined sewer area, installed by a licensed plumber with the needed permits. Devices installed before the program started don't qualify.

Spring and the river

Snowmelt plus rain is the Manchester flood. The worst rain at the airport came in May 2006: 8.52 inches in three days ending May 15, 2006. The Merrimack at Goffs Falls crested at 19.87 feet that week, well past the 15 foot moderate flood stage, and federal flood insurance claims in the ZIP codes we cover jumped to 185 that year and 116 the next. Over 88 years the river's highest stage passed the 11 foot minor flood stage in 33 of them, most recently December 19, 2023.

Highest river stage each year, Merrimack River at Goffs Falls (feet)

Source: USGS annual peaks, site 01092000, 1936 to 2023. Flood stages: NWS gauge GOFN3 (minor 11, moderate 15, major 17 ft).

What gets thrown out

After sewage or flood water, porous materials usually can't be saved: carpet and pad, drywall the water touched, upholstered furniture. Concrete and studs can usually be cleaned and dried. Finished basements cost the most, because everything on the floor and the bottom of every wall is porous.

Before the next storm

A sump pump that loses power in a storm is no pump. A battery backup pump is the usual fix.
Check that the discharge line drains away from the foundation, and isn't frozen shut in a cold snap.
Raise the furnace and water heater off the slab.

Questions Manchester homeowners ask

Does homeowners insurance cover a flooded basement?

It depends on the water. A burst pipe is usually covered. Flood water and groundwater usually aren't; the NH Insurance Department has said most homeowners policies exclude flood damage. Sewer backup usually needs an endorsement. Even a flood policy covers only some items in a basement, per FEMA's basement fact sheet.

Is sewage cleanup something I can do myself?

It is not a good DIY job. Sewage carries bacteria, and porous materials it touched usually have to go. Keep children and pets out, don't run the HVAC if the air handler is in the basement, and let a company remove and sanitize.

How do I know if my street has combined sewers?

The City of Manchester publishes a map with its CSO 50/50 Sewer Backflow Program. Manchester EPD can confirm whether a property is in the combined sewer area.