[Diane Mallon]

I hear my septic cover thumping when someone is taking a shower or dishwater running. I he had my septic pumped within the last 6 months and don't know why it's thumping. An ideas?

[massplumber2008]

Hi Diane

Are you sure you need to pump out your septic tank? Is it possible that your septic tank has a CHECK VALVE and a sewage ejector pump under the lid... when the tank fills enough the pump turns on and ejects solid and liquid waste... the clunking sound would be the check valve (back flow preventer) closing back on itself to prevent any back flow of waste water into your septic tank.

If your tank doesn't have a sewage ejector then let us know and we'll see what else we think, OK?

Mark

[ballengerb1]

Which cocver are you talking about, the one outside above the tank?