Every morning between 5-6am there is a loud moaning noise that comes from the basement. Almost sounds like a lawn mower. Whenever we turn on the water in bathroom sink or flush the toilet it makes this loud sound. I don't know what it could be. And it only does this in the morning. It started doing this when one day the water in bathroom sink stopped running. I took the filter off the faucet and there was a small black looking pebble. The water started running fine again, then I started to hear this noise the next morning.

What could this noise be and how can I fix it?

Is there a basement bathroom? Cheers, Tom

No, there's no bathroom in basement. Just the water heater. It seems to only make the noise in the morning.In order to get it to stop we have to either flush the toilet again or run the water in the bathroom sink. After around 7 or 8am we don't hear the noise again until the next morning. Thanks

This is one of these problems where, like smells, you have to be there to track it down. Last try! Is the water heater gas or electric? I may have a answer. NCheers, Tom

I 'll take all the help I get with this. The water heater is gas. Thanks

Small black pebble huh? Let's take a hard look at the water heater. Sounds like something's down in there. Let me show you how to flush out your water heater.
For long life and fewer troubles you should keep your heater clear of mineral build-up by flushing on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. It. In a gas hot water heater it's possible for minerals to build up in the bottom of the tank. When the burner comes on it can turn the water under the mineral build up to steam. The steam escaping from under the build up can make strange noises.
Let me know it it sounds better after you flush it. Good luck, Tom

I haven't had the chance to thank you. But I haven't heard the noise in weeks. Thank you so much for your help. I was beginning to run out of options. I'll be sure to recommend this site to friends.