Black Tank Flush Pressure

[jfbritt]

I have a Montana 5th Wheel with a black tank flush connection. I will assume there is an anti-syphon valve somewhere between the water line connection and the black tank. When connecting the city water to flush the black water tank, what is the maximum pressure that can be used when flushing? Can you allow the city water to flow without any pressure control?

[DQDick]

Yes you do have a backflow preventor and in most Monty's it's under the bathroom sink. If the pressure is ok for your rig it should be ok for the black tank flush. I've only been two places that I wouldn't hook up the flush without a regulator and both had water pressure over 100psi.

[Daryles]

This one is a plastic one similar to the stock one installed. It says it is rated to 125 psi

https://www.amazon.com/dp/B07P75Y1MR..._z.mJFbWW3NRS7

[boisesmith]

Most seasoned members suggest removing the valve or replacing it with a brass model. Too many horror stories of an original equipment valve failing.

[BB_TX]

If you are using a water pressure regulator at the faucet then use a Y connector off that to connect the flush hose. The piping connections may not be rated as high as the anti siphon valve itself. No need to risk it.

[beeje]

Originally Posted by boisesmith

Most seasoned members suggest removing the valve or replacing it with a brass model. Too many horror stories of an original equipment valve failing.

The really seasoned members remove it and throw it away and plumb the lines together. You have a better chance at being struck by lightning than contaminating the water supply because the government mandated BS device has been removed. WAY too many campers have been flooded because of that leaking valve.