Do I need a sump pump?

Not every basement does. Here is how to tell which kind you have, before you spend money on either answer.

Plenty of houses have never needed a sump pump and never will. Plenty of others have a pit sitting empty for eleven months and indispensable for the twelfth. The question is worth answering deliberately rather than by default.

You almost certainly need one if

• There is already a pit in the floor. Somebody installed it for a reason, and that reason has not gone away.
• The basement has flooded before, even once, from groundwater rather than a burst pipe.
• You see a water line, staining or efflorescence on the walls near the floor.
• The house sits at the bottom of a slope, or below the neighboring grade.
• The water table is high locally. Neighbors with pumps running after rain is the clearest possible evidence.
• The basement is finished, which changes the cost of being wrong by an order of magnitude.

You probably do not need one if

• No pit exists and the basement has been dry for decades, through storms and spring thaws.
• The house sits high and well drained, with the ground falling away in every direction.
• Local houses do not have them. Building practice in an area tracks the water table closely.
• The only dampness is humidity, with no liquid water. That is a dehumidifier problem, not a pump problem.

#1If the answer is yes

Zoeller M53 Mighty-Mate

The default first pump: cast iron, well documented, and supported everywhere.

8.9/10★★★★★Our editorial score: 8.9 out of 10

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Specifications, as published by Zoeller

Type	Submersible, cast iron
Horsepower	3/10 HP (sold as 1/3 HP)
Electrical	115 V, 9.7 A, 60 Hz
Discharge	1-1/2" NPT vertical female
Switch	Integral vertical float, on at 7-1/4", off at 3"
Solids handling	1/2"
Shut-off head	19.25 ft
Flow, by lift	2,580 GPH at 0 ft · 2,040 GPH at 10 ft
Warranty	Three years

If you already have a pit and no pump, or a pump that has failed, this is the straightforward answer.

What it gets right

• Cast iron
• Published flow curve
• Parts available everywhere

Where it falls short

• Heavy
• Needs pit width

Specifications from Zoeller M53 (53-0001) specification sheet.

#2If the answer is probably not

Basement Watchdog water alarm

A floor alarm costs almost nothing and tells you if you were wrong.

8.9/10★★★★★Our editorial score: 8.9 out of 10

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Specifications, as published by Basement Watchdog

Type	Standalone basement water alarm with a floor sensor
Use	Sits beside the pit, not in it, so it only sounds when the pit has already lost

If you decide you do not need a pump, spend a fraction of one on an alarm. It is the cheapest way to find out whether the decision was right.

What it gets right

• Cheap
• No network needed
• Turns an unnoticed event into a known one

Where it falls short

• Local alarm only
• Does nothing about the water itself

Specifications from Amazon listing (search).

Finding out for certain

1. Step 1Look during the worst weatherNot on a dry Tuesday. Go down during a heavy storm or a spring thaw and look at the floor, the wall-floor joint and the corners.
2. Step 2Check for an existing pit, even a covered oneOlder houses sometimes have a capped pit under a flooring layer or behind stored boxes.
3. Step 3Ask the neighborsThe single best source of information about your local water table is the person next door who has lived there twenty years.
4. Step 4Put an alarm on the floorIf you are unsure, spend a few dollars rather than a few hundred, and let the house tell you over the next year.