What Is a Sump Pump Weep Hole?

There's nothing worse than having water accumulate in your basement after a heavy rain. Although you have a sump pump, it seems to be doing nothing. You've heard that a sump pump weep hole will make the pump work properly, but don't understand why this helps.

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What Is the Purpose of a Sump Pump Weep Hole?

The sump pump weep hole's purpose is quite simple: to prevent an air lock between the pump and the check valve that can prevent the pump from pumping. So, how does a sump pump weep hole work?

The sump pump has a check valve to stop water from running back into the sump if the pump isn't running. But when the pump stops, the water under the check valve and pump drains out, creating a partial vacuum or air pocket between the check valve and the pump.

When the sump pump starts, it can't create enough pressure to force the air through the check valve, and the pump runs dry. The purpose of the weep hole is to provide an easy path for the air to escape, allowing the pump to fill with water and start pumping.

Does Every Sump Pump Need a Weep Hole?

No, not every sump pump requires a weep hole. If the pump design allows it to self-prime, it doesn't need a sump pump weep hole.

Self-priming sump pumps come in several styles. One is like a standard sump pump, except the impeller blades have one or more small holes that allow the water to flow into the pump body. When you start the pump, it's partially full of water and can drive the air through the check valve and pump water. Another type has a top-mounted suction inlet. This means there's always water inside the pump's body, and it's self-primed.

Where Is the Weep Hole Located?

A sump pump weep hole is a small hole drilled into the discharge pipe between the pump and the check valve. The position of the hole isn't critical, provided it’s a few inches above the pump outlet. The recommended sump pump weep hole size is between 1/8th and 3/16th of an inch in diameter. You should make the hole with the drill pointed upward at a 45-degree angle to the vertical sump pump pipe. Some sump pump check valves have a provision for a weep hole in their body, so all you need is to drill or open the hole.

Why Is My Sump Pump Spraying Water From the Weep Hole?

When the pump runs, you'll see a sump pump weep hole spray coming from the pipe. It's an unavoidable consequence of drilling the weep hole to let the trapped air out of the pump. It's nothing to worry about, as the volume of water coming out of the hole is a fraction of what's being discharged from the pump. You want this water to run back into the sump pit, so that's why you drilled the sump pump vent hole at a vertical 45-degree angle. If you haven't done that, the water can spray horizontally or upwards and leak out through the sump pit cover onto the basement floor.

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Why Do I Need a Sump Pump?

Many people wonder why they need a sump pump at all. Their thinking is that with modern building methods, it's possible to seal the basement properly. This is partly true but practically difficult in areas that have a lot of rain or snow or a high water table.

You may be able to dispense with a sump pump in areas that have little rain. Then again, in most parts of North America, the height of the water table in the ground is above the bottom of your basement. This is particularly the case during the rainy season and spring thaw. Also, the basement could be flooded by heavy rain.

The natural movement of water in the soil exerts pressure against your basement walls and floors. Unless the damp sealing is perfect, water can seep through the basement walls and concrete floors. This is the reason most homes have foundation drains that collect the groundwater and discharge it into your basement sump.