Mansfield toilet really hard push the flush valve

All the toilets in my house became really hard to flush. I myself need to use almost all my strength to push the flush valve. It's impossible for my kids to do it. The toilet is Mansfield No. 160. I had planned to replace all three toilets in the house completely since I felt frustrated every time my kids ask me to help them to flush the toilet. But somewhere I read (sorry, I forgot where) that it may be caused by the old seals.

So I went to Home Depot and bought three seals labeled for Mansfield #120 (each costs me $1.95 at the time). I followed the instructions, replaced the old seals. Now even my 3 years old daughter can easily flush the toilet. I actually scanned the front and back of the item sold at Home Depot.

And if your toilet is really hard to flush, may be it's due to the same reason. Why not give it a try?

fig. 1 front image

fig. 2 back image