Dear Angie: We've had to replace several sump pumps in just a few years, and I'm wondering why.

We initially had a pump with the float on a rod, but the first time our basement flooded, it was because lime scale had built up on the float switch and prevented the float from sliding. We switched to one with a balloon type of float switch, but the switch sometimes gets stuck because our sump pit is very narrow. Because our sump pump runs so often, the switches frequently go bad.

Is there a type of sump pump that would work best in a narrow pit? Is the narrow pit the reason the sump pumps are running often? We have a water- powered backup pump, but do you have any advice on how we can address this issue so we're not replacing the main pump every year? — Amy K., Avon, Ind.

Answer: A smaller or narrow pit will fill up with water faster than a larger pit, thus causing the sump pump to work more often. A sump pump typically lasts five to seven years. Like most devices, though, the more the pump works the faster it wears out.

Plumbers I've spoken with don't recommend pressure switch or float switch pumps for narrow or shallow pits. These pumps are activated by the amount of water in the pit. If you have a smaller pit area, the water will fill quickly and the level will be high before the pump kicks on. In heavy rain, if the water level is already high in the pit, the pump might not be able to keep up. That could lead to flooding occurring quickly. Plus, like you said, in a narrow pit, the switches can get stuck in the pit.

You might consider a pump with a vertical switch, which would keep the float from getting stuck on either side of the pit.

You also mentioned you had scale buildup on the pump that caused a failure. Cleaning the pump every few months with a solution of white vinegar mixed with water can help reduce that scale and keep the pump clean and in good working order.

I also recommend checking your sump pit periodically for debris such as mud, rocks and sticks, which can cause the pump not to operate correctly.

It's great that you have a backup pump. Every homeowner with a sump pit should, but if your backup is being used often, you'll want to make sure it has the capacity to pump out the same amount of water as your primary pump. Often, backup pumps are substantially smaller, so they don't pump enough water or don't pump it out fast enough to avoid flooding.

If you plan to stay in the home for several years, you could look into having the small pit removed and a bigger pit installed, or having a second, overflow, pit installed with a second pump next to the original and having the two connected. A professional with sump installation experience can help guide you in deciding if this option is best for you. If you're replacing pumps every six months, at $150 to $200 a pop, it could be the best solution in the long term.

Angie Hicks compiles the best advice from the most highly rated service pros on Angieslist.com to answer your questions. Ask Angie your question at askangie@angieslist.com.