Dump Valve Size and Why we Don’t Make an 1.5″ Valve

Have you ever wondered why a lot of RVs use a small 1.5″ valve on the gray water tanks? We spent considerable time asking RV manufacturers that question a number of years ago while in the process of designing a true 12vdc electric dump valve. (Prior to this all other electric valves were not really electric valves—they were manual dump valve actuators.

We got a number of answers including;

1. It costs less for both the valve and the pipe and parts.

2. The gray water doesn’t have solids so a smaller pipe and valve works fine.

3. So the customer knows which valve does what.

4. Because we always have.

At first this sounded reasonable but the high cost of tooling to create injection molded parts and not being convinced a 1.5″ valve on the gray water tank was correct, we did further testing. We found first and foremost using a 35 gallon tank, it took 2.56 times longer to dump the tank through a 1.5″ valve than it did through a 3″ valve!  The thought occured to me as an RVer; why would the manufacturer want to keep its customer in a place they do not want to be for longer than they need to be?

DO YOU WANT TO WAIT FOR THIS?

slow drip hose - gray water

As an RVer I know that all of us dump the black first and the gray second, so we clean the inside of the hose. The problem is that when it is done using 1.5″ piping, the water running down the hose is a trickle not a flood, as it is with 3″ plumbing. We also noticed that as the water drained slowly through the 1.5″ pipe the scum that forms on the top of the gray water adheres to the sidewalls of the tank, much more so than it does when using 3″ pipe. In addition the whirlpool or tornadic effect inside the tank pulls the scum out much better as it exits the tank. With an 1.5″ valve this action is almost undetectable.

OR WAIT FOR THIS?

water rushing onto rocks - gray water

The decision to not spend the tooling money to create a valve that didn’t have any advantage to the customer, became pretty easy.

What to do? Educate the RV manufacturers on our findings and provide a reducer flange so folks wanting to retrofit their existing RV could do so.

reducer flange small

We designed the flange so it will fit into an 1.5″ pipe easily, see directions HERE

If you have any questions, as always we are here to assist you, whether you want to switch from 1.5″ to 3″ or completely redo your waste configuration.
Call 877 787 8833 toll free or email us admin@drainmaster.com

Need to order a 1.5″ Reducer Kit? Click Here

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