Thank you all for answering.
I think the problem may have been fixed. At least, that's what I'm hoping and praying for. My dad came to my house and heard the noise, went through all the bathrooms. One of the bathrooms on the north side of the house is never used because it's always very cold that part of the house. The toilet bowl was all dried up, so he flushed the toilet and there's now some water in the bowl. He also turned on the bath tub and sink faucets and let it run for a couple of minutes.
I haven't heard the noise from anywhere since then - granted I haven't done any laundry yet. But at least, the noises coming from the kitchen is gone.