Floor Drain: When You Want Things to Go Down the Drain


Table of Contents


Let’s start with the basics: what is a floor drain, and what’s it for? A floor drain is an opening in the floor of a basement that connects to a sewer pipe beneath the floor. It makes it possible to divert water from the basement, to prevent water accumulation. A basement drain can protect to some degree against water damage.

Installing a Floor Drain

Location, location, location

The location chosen for the drain is important: generally speaking, it should be located at the lowest point of the basement floor. A couple of other considerations come into play also, however. The location of appliances such as a water heater or basement bathroom fixtures will also come into the picture: in those cases the drain might be located near to those potential sources of water.

As the floor drain will also be connecting to the wastewater plumbing beneath the floor, placement of the drain should also take that into consideration. Other things being equal, locating the drain near to where it can be attached to the underfloor plumbing will reduce the amount of concrete work and excavation involved.

If the basement does not have plumbing pipes, another way to remove water will need to be found; usually a sump pump is a solution.

Opening the floor

Once the location for the drain has been determined, and the routing to the connection point established, then the floor is cut where the drain will be located. A hollow drill hole cutter is used to cut where the drain will be, with the size of the hole cutter matched to the size of the PVC piping that will be used.

Drill down to the depth far enough to fit pipes in horizontal runs.

Cutting the floor

Next, a circular saw is used to cut the floor slab to open the path where the piping trench will be dug. Take care at this point not to cut into pre-existing pipes or electrical cabling.

Connecting to the sewer

The drain pipe is led from the drain to the sewer and seated on a bedding of gravel and sand.

Now, the drain piping is connected to the sewer. If there is no sewer piping available, the drain will need to be led to a well-located below the floor of the basement, and a sump pump can be installed.

The drain end of the piping should be left a little bit above grade, so that it can be accurately cut to length once the floor has been re-poured, and before the drain cover is fitted.

Closing it all up

WAIT! Before enclosing the newly-laid piping, check your work for leaks.

OK, now the pipes are back filled with crushed rock, and the trench is filled with concrete. Then the pipe is trimmed and the drain cover is fitted.

Other drain considerations

The floor drain, connected as it is to the waste line, is a potential source of odours rising from that pipe into the basement. To prevent this, a couple of elements should be added to the system. First, the drain should pass downwards through a trap, before running to its connection point on the waste line (see diagram).


The trap serves to hold an amount of water in the pipe between the waste line and the drain grating. This water makes a trap seal that prevents smells from rising from the waste system. An added feature is a trap primer line, which introduces a small amount of water into the trap from time to time, to maintain the trap seal. The trap primer line runs from a nearby source of water, such as a laundry tub, to the grating side of the drain trap. When water is run into the laundry tub, a small amount is diverted into the drain trap.

For professional floor drain installation, contact Master Drain today.

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