Sump pump or ejector pump? or both?

[dreaminggates]

Hello there, fellows. I'm posting here because I hope you guys can help me figure out what I have. (Pardon my newbie-ness, but this is my first house and the first plumbing I've ever looked at in my life.) I have a basement bathroom with a sump pit in it. I know I have an ejector pump because when we run the shower, I can hear it kicking on (loudly). The question I have is... why does it also kick on during rainstorms? I know the sewage and the groundwater-runoff systems are supposed to be separate... so what's going on here? Do you think it's likely that I have a sump pump and an ejector pump, both contained in the same sump pit? Is such a configuration possible / normal?

Thanks for your insight!

Edit: P.S. - We're on a well with drainage field, not public sewer, in case that makes a difference.

[jadnashua]

My guess (I'm not a pro) is that the water below the slab is draining into the ejector (maybe by design). Now, this may not be a great idea, as it can dilute the leach field and disrupt the normal bacterial action there (it could also wash solids into the leach field). Now, you may not ever have the volume to create this problem (I know at my mother's house, this would be a major problem!). That's the only reason I can think of that would be related to it running when it rained.

[Deb]

Yes, you could have two basins and two pumps in the same pit. However, you really need to know for sure. If this is a new home, you should be able to call your contractor and ask to have the plumber go over this with you. If not, you will most likely need to hire a plumber to check this out and explain your system to you. I am surprised that most people do not even know where their main water shut off is or if it even works.
The question, ultimately, is where the rain water is being pumped. Since you are on a septic system, it is VERY important to check this out. Your drainage field can become saturated It is generally relatively easy for a plumber to figure out what is what and where it goes.
Deb
The Pipewench