DUNBAR
Could be a faulty fill valve in the toilet.
It could also be a sign of high water pressure in your home.
You posted another thread discussing thermal expansion, with a leaking T&P, you might need to check your water pressure to make sure it is not high. Anything over 60 is considered high and when reaching 80, codes usually are enforced in most areas.
View this link: very important and useful knowledge..
http://www.wattscanada.com/faq/regulators/main.html
