I'd imagine the pump has a check valve, which would prevent anything coming back in from the sewer side. You can ask to confirm if it does.
It is a lot different than a septic tank. This pump just makes sure it all gets out to the sewer, a tank holds it and lets it out into a drain field, it doesn't go to a sewer.
They are pretty simple. There's a small pit in the basement that all your drains run into (although if it's a two story house, it's possible for the second story to be entirely gravity drained, and if it's an option to do that, take it, because you will be glad you did when the power is out).
Inside the pit is a sewage ejection pump and a float switch. When enough liquid is in the pit, the float switch will turn on the pump. It will pump the sewage up a big pipe and out of your house. When the level in the pit is low enough, the float switch turns off the pump. They normally only run for 5-10 seconds at a time. There is a check valve on this pipe just above the pump which keeps any of this from flowing back into the pit when the pump turns off.
Potential issues:
- When the power is off, the pump won't run, so you can't use any water (or very little). If you do, the pit will eventually overflow.
- Similarly if something goes wrong with the pump (unlikely) or the valve (more likely) then you can potentially get an overflow. It's not as bad as it sounds, as the top is all basically water. I would set up a leak detector that sounds an alarm if this happens.
- If you let a lot of grease go down the drain (and even if you think you don't you probably do) it will condense into fat balls that gradually grow to quite large size and will eventually interfere with the switch or pump. So you have to clean these out every so often. A bit smelly, but easy enough to do.
They are not much trouble, but it is one more thing to worry about. It is definitely better to have drains that run entirely on gravity, but it's not that big a deal either.
I'd imagine the pump has a check valve, which would prevent anything coming back in from the sewer side. You can ask to confirm if it does. It is a lot different than a septic tank. This pump just makes sure it all gets out to the sewer, a tank holds it and lets it out into a drain field, it doesn't go to a sewer.
I live next door to a house with a sewage pump. Second owner - still nothing but trouble.
They are pretty simple. There's a small pit in the basement that all your drains run into (although if it's a two story house, it's possible for the second story to be entirely gravity drained, and if it's an option to do that, take it, because you will be glad you did when the power is out). Inside the pit is a sewage ejection pump and a float switch. When enough liquid is in the pit, the float switch will turn on the pump. It will pump the sewage up a big pipe and out of your house. When the level in the pit is low enough, the float switch turns off the pump. They normally only run for 5-10 seconds at a time. There is a check valve on this pipe just above the pump which keeps any of this from flowing back into the pit when the pump turns off. Potential issues: - When the power is off, the pump won't run, so you can't use any water (or very little). If you do, the pit will eventually overflow. - Similarly if something goes wrong with the pump (unlikely) or the valve (more likely) then you can potentially get an overflow. It's not as bad as it sounds, as the top is all basically water. I would set up a leak detector that sounds an alarm if this happens. - If you let a lot of grease go down the drain (and even if you think you don't you probably do) it will condense into fat balls that gradually grow to quite large size and will eventually interfere with the switch or pump. So you have to clean these out every so often. A bit smelly, but easy enough to do. They are not much trouble, but it is one more thing to worry about. It is definitely better to have drains that run entirely on gravity, but it's not that big a deal either.
Thank you for the detailed explanation. This sounds really really awful to deal with.
Eh, it wasn't that bad. In 15 years only ever had a couple of issues with it. 99.9% of the time, you barely even know it's there.