toilet water valve

I changed the valve and used that white hose from the valve down to the tee on the floor. Also hooked up a shutoff in case something leaks in the future so far so good no leak.

I finally replaced the leaking valve on my Style Plus. The old valve had fine spider web cracks in it. I found out why when I went to reinstall the toilet and the supply piping didn't line up. BF had simply forced the pex into position, keeping a steady force on the valve. A little trimming of the pex took away the bind. If it leaks again, I'll look into a flexible hookup line, but I believe this will last much longer than before.

I found a new valve today to have on hand when I decide to change it, I won't lose any sleep over having it hooked up with a bad valve that still works.

Basically a one way valve. The purpose is to keep contaminated water from potentially back flowing into source, however unlikely.

https://www.thetford.com/parts/rv-toilets/
Identify toilet model and parts (some toilets VB/flush valve are separate, some are combined in one unit-) then search on-line for parts.
I would not leave toilet connected to water source if I knew valve wasn't functioning or disabled.

The explanations provided by phil-t/opnspaces and Old-Biscuit are contrary. Can someone else chime in on the purpose/function of this vacuum breaker?

I guess that shutoff I installed will come in handy,just can't figure out how water can be sucked up from the bottom of the toilet. New valve will have to wait can't even go to an rv store and match it up.

Gary3 wrote:
Well it can,t suck anymore its plugged for good.

Actually now that it's plugged it definitely can suck toilet water back into your fresh water system.

Yes it would have to be an unlikely event of the bowl full of water so the fill hose in the bowl is covered. Then at the same time the fresh system has to lose pressure so that water starts flowing back toward the tank. If that happens you do not have a vacuum breaker to prevent siphoning water from the toilet bowl back into your fresh system.

Yes unlikely, but safety things are there for a reason. The manufacturer doesn't just put anti-siphon valves on the RV to pad their wallets.

Which Thetford model? I just noticed my Style Plus is leaking from the supply side flush valve.

Water goes to toilet water supply valve then goes up to the Vacuum Breaker then down into toilet when you flush
Hole in top of vacuum breaker closes off from water pressure

Then after flushing and toilet valve closes the vacuum breaker hole opens and allows water to drain down into bowl...that is where the water in bowl comes from

Water in bowl is a vapor barrier......stops black tank odors from coming backup thru toilet bowl seal
Water in bowl keeps bowl seal from drying out...leaking

Vacuum breaker is there by Design....replace it.

Well it can,t suck anymore its plugged for good.