I am a noob here but I thought I'd share a brain fart I had in researching a replacement for my sump pump and see what others think.
Imagine you're designing a sump pump from scratch. If reliability is ones primary requirement, I would *not* choose a design that has the electrical motor and switch to turn it on submersed in the corrosive and short-circuiting environment of the sump pit unless I had no other choice. Even if they are well sealed, this design assumes the risk of the seals failing over time.
Instead I'd choose a design that avoids this risk and has these critical and water adverse components in an environment that is more friendly to metal and electronics, like outside the covered sump pit as a pedestal pump allows.
If engineered correctly, the switch and motor in this less challenging environment should be reliable and not suffer premature burnouts or anything like that.
This thinking appears to be supported by comparing actual lifespans, at least according to some:
"The pedestal pump has a longer life span. Water does take its toll on a submersible pump. Pedestals are known to last 2 to 5 times longer and are cheaper than submersible pumps." http://EzineArticles.com/3924023
"Because [submersible pumps] are frequently under water, though, they do not last as long; the average life span is between 5 and 15 years. Pedestal sump pumps are less expensive, and can last much longer than a submersible pump; in some cases, a pedestal pump will run for up to 30 years." http://www.ehow.com/how_5755593_select-sump-pump.html
"Corrosion-resistant materials, such as cast iron and stainless steel, will keep your pedestal sump pump in good working order for years. Its expected lifespan is between 25 and 30 years, depending on the manufacturer’s quality of material and craftsmanship, and on frequency of operation. Submersible pumps usually last between 5 to 15 years." http://www.sump-pump-info.com/pedestal-sump-pump.html
Despite this, submersible sump pumps seem to be more popular and have a reputation with many people as being the most reliable.
If you were shopping for a fridge or car and knew a brand that lasted 40% longer that would be something significant to think about and influence ones decision. But we're talking 200% - 500% longer here if those numbers above are correct. That's extremely significant.
I am wondering what other people's thoughts and experiences are here. Paying much more money for a submersible that on average has a significantly shorter lifespan than a pedestal seems like an odd choice for such a critical device unless noise and other factors are more important to one than reliability.
Even if the basement or crawl space was extremely dusty or damp, making it unsuitable for the unsealed pedestal pump motor, I would just want to find a sealed version (with appropriate air cooling) and stick with the pedestal design, not seal it and then submerge it and the electrical switch to turn it on under water.