Fixing Constantly Running Dual Flush Toilet Fluidmaster Refill Valve Without Any Complex Tools Or Parts. A constantly running Toilet can cost a huge amount of money in wasted clean water, here is a simple emergency plumbing fix I use.
If after carrying out the instructions in the video you discover that the fluid master inlet valve seal washer is perished or deformed in such a way to make it useable then the cheapest solution is to purchase a replacement. They are really cheap and around 10% of the cost of a new unit and could save over 30 mins and a wet floor from trying to replace the entire unit.
In my case it was the Fluidmaster 242 Replacement Seal