Chinook RV

Does anyone know the exact size of the fresh water tank drain valve? I want to say it's 3/8", but it could be 1/4". Just want to try to find out before I order one, and couldn't find it on here after searching. Thank you!

You mean the petcock valve that drains the water tank to under the coach? Isn't all the PEX are 1/2 inch diameter, so the valve is also 1/2... someone will need to confirm, however.