Idle Toilet Squeals Every Morning Beginning at 4:15

[TheBigScat]

The thread title pretty much says it. It's a continuous squeal similar to the sound of a smoke detector or bedroom alarm, and it's loud enough to be heard throughout my two-story home. From what I can tell, it generally begins around 4:15 a.m., and it usually lasts until around 5. Flushing the toilet ends the sound, and it does not occur at any other time of day or when flushing the toilet. The toilet is not used much, and I haven't noticed a leak on the floor. Please advise so I can get back to sleeping well! Thank you!

 

[Twowaxhack]

Replace the ballcock and flapper/flush seal.

 

[FishScreener]

Mine will do it if I bypass the pressure reducing valve. Are you on a city water supply?

Most systems pump to reservoirs in the early morning, when electricity is least expensive. To save on the power costs. So, the pressure is highest in the early morning, and drops through the day, as people use water which starts at about 0500.

The other potential is transient pressure spikes caused by sprinklers coming on and off. The downstairs toilet in my folks house had issues with the fill valve, until Dad installed a surge arrestor on his sprinkler manifold.

If you have a pressure reducing valve, it could be wearing out and letting too much pressure into your house.

 

[TheBigScat]

Thanks to both who responded. I will try the fix Twowaxhack suggested, and FishScreener's post probably explains why this is only happening in the pre-dawn hour. Much appreciated!