[Dhead]

3/8'' with 4 1/4"

One more

[Richard]

Don’t get sidetracked by what size NPT is on the manifold. Buy the compression fitting that has your tube size on one end and the NPT size you need on the other.

[Dhead]

Today was a good day - I got under the coach in the back (with two 20 ton jacks). First was to orient the tanks and make sure the drains work.
As was said, the front two tanks are big tanks in line with the frame and the other two are smaller and farther back centered between the frame.
All told there was less than a half teaspoon from all four - only two drained. The front passenger side (black water with oil, enough to get both hands black) and the rear tank more water but still not much.
As the temperature has risen the 'add on' pancake compressor runs less than 30 seconds, generally 25 to 30 minutes - and that is with the Valid manifold still leaking. I have the new aluminum manifold - still need a few more pieces and parts...

[Richard]

Here is a quick and high payback project for you. Remove the petcocks from those drain tanks and replace with DOT fittings. Run the DOT nylon air hose to a convenient location. Terminate the lines with stainless quarter turn valves. Run an exit line from the valve to under the coach frame.

Now you can stand on the ground, and drain each tank while watching what comes out.

Well that is, unless you enjoy a rust water and oil shower a couple of times a year.

[Wanderman]

I heard that's good for the skin

[BusNit]

Keeps me moisturized every so often! Richard, that's a great idea and as dumb as I am, hadn't even thought about doing that! Perhaps it's the desire for self punishment?! One more thing added to the list.

[Dhead]

I will make that the next job after I install the replacement Valid Slide manifold (and the other non DOT fittings in there).