Monsoon season and your sump pump: a Scottsdale guide

What a sump pump does, and when it matters

A sump pump sits in a pit at the low point of a basement or below-grade space, and when water collects in that pit, a float switch turns the pump on to send the water away from the house. Most of the year, in dry Scottsdale, it has nothing to do. Its entire purpose is concentrated into the few storms a year that overwhelm the ground's ability to absorb water.

Those storms are the monsoon season, roughly July through September, when a single cell can drop an inch of rain in an hour onto ground baked too hard to soak it up. Runoff finds the low points, and for a home with a basement or below-grade garage, the sump pump is the difference between a dry space and a flooded one. The catch is that the pump has to work perfectly on the one day it is needed, after months of sitting still.

The silent failures to check for

Sump pumps fail quietly, because all their failure modes happen while the pump is idle and unwatched. The float switch can stick in the down position sometime during the dry months, so it never tells the pump to run. The check valve that keeps pumped water from flowing back can quietly stop holding. The motor can seize from disuse. None of these announce themselves; you find out when water is rising and the pump sits silent.

That is why a sump pump cannot be a set-and-forget device in a climate like this. The long idle stretch that makes it easy to ignore is exactly what makes it likely to fail when called upon. A sump pump service check, or a simple homeowner test, is what turns an unknown into a known before the storm, rather than during it.

The test that takes five minutes

You can test a sump pump yourself before the season, and it is worth doing every year. Pour a bucket of water into the pit slowly and watch. The float should rise, the pump should switch on, the water should pump out, and the pump should switch off when the level drops. If any part of that sequence does not happen cleanly, the pump needs attention before you rely on it.

While you are there, look at the discharge line to make sure it carries water well away from the foundation and is not blocked, and listen for a motor that runs rough. If a flooded space would be costly, a battery backup is worth adding, because the same storms that flood are the ones that knock out power, and a pump with no power is no pump at all.

When the pit fills without a storm

Here is a Scottsdale wrinkle worth knowing. If your sump pit fills or the pump runs when it has not rained, the water is coming from somewhere other than the weather. That can point to groundwater, but it can also point to a plumbing issue nearby, an irrigation line or a hidden leak feeding water toward the low point of the house.

A pit that cycles in dry weather is worth investigating on its own, because a pump masking a slow leak means you are paying to remove water that should not be there in the first place, and the underlying leak keeps working. Sorting out whether the source is groundwater or a leak tells you whether you have a drainage question or a plumbing repair, and they call for different fixes.

Where the discharged water should, and should not, go

A sump pump is only as good as where it sends the water, and this is a detail that catches people out. The discharge line should carry water well away from the foundation and release it where it can drain off, not right beside the house where it simply soaks back down to the pit and gets pumped again. A discharge that loops water back to the foundation makes the pump run constantly and never wins.

It also should not dump onto a neighbor's property or into a spot that causes erosion or a code issue, so the routing deserves a moment's thought rather than the shortest possible pipe. During the dry months, check that the discharge line is clear and has not been crushed or blocked, because a pump that runs into a clogged line is a pump that fails when the storm hits. If the pit fills in dry weather, that points to something other than rain, sometimes a hidden leak feeding the low point, and it is worth investigating on its own.