Toilet valve sucking water out of bowl. Refilling bowl every few min.

[Nichols]

I noticed the tank was refilling the bowl every few min. Indicating a leak. I replaced the flapper with no change. I then noticed that after the bowl fills the fill tube is sucking water possibly out of the bowl and this is only fixed by pulling the line out of the overflow tube to stop the suction. Should I replace the rest of the plumbing? What is the cause? I have adjusted the depth of the line into the tube without a change... Thanks for your help. A roofer did cover an "old" vent on my roof a few months ago. Would this have caused a problem?

 

[IFIXH20]

The fill valve to flush valve tube can't suck water out the bowl. The fill valve to flush valve tube is syphoning due to being below the water level in the tank, attach the tube to the top of the flush valve (which will be above the water level in the tank),this will stop the syphoning.

 

[IFIXH20]

Test your tank for leaks with food color. Mix a dark color food color with water, flush the toilet, when flapper drop/seat after flushing, pour food color in tank as it refills. (do not get any in flush valve overflow) Let toilet set for 15-30 min, If color shows up in your bowl - Your still getting water through the flapper/flush valve seat or the flush valve gasket is bad.