My toy hauler didn't have a fresh water drain valve when we picked it up last spring. The dealer got permission from the factory to install a valve. I picked it up last week and was surprised to see that they just installed a small 1/2" valve like the shuttoff to a residential toilet. I assumed it would be a large valve like the gray tanks. That's kind of irrelevant to my puzzler though.
I was surprised when I first picked up our trailer because the gauge showed that the tank was nearly full. I wouldn't have expected the dealer to fill the tank. But maybe the gauge is just broken (very likely). I couldn't ever test this, because I couldn't empty the tank and start from scratch. So for every dry-camping trip, I would just add what seemed like sufficient water and cross my fingers.
Now with the valve installed, I drained the tank empty and then refilled it with a meter attached to the hose. I could only get 60 gallons into the tank though, half of the advertised capacity.
Here's more info in the email I sent my dealer:
Hi (nice service writer),
Thank you again for installing that fresh water drain valve. I have a mystery on my hands now though. Maybe you can help me figure it out.
Here’s the sequence of events:
• I opened that valve and let it drain for hours. (It takes forever to drain that much water through a 1/2" valve.)
• I checked the level indicator and it showed that the tank was 2/3 full. This was strange, but not completely surprising because I had suspected this indicator wasn’t functioning all along. I had never been able to test it before since I couldn’t drain the tank.
• I attached my meter to my hose and slowly filled the tank. My goal was to fill it with 100 gallons. I shut off the water in 20 gallon intervals to allow any built-up air to breath out.
• At 60 gallons, the tank started to drain through the blue overflow line near the front axle. It looked like it created a siphon and drained for a few minutes.
• I let it sit for about 20 minutes and then slowly added about five more gallons before it overflowed again. I’m pretty certain that the amount that I was able to add back in was the same amount that siphoned off the first time, so the tank should have only 60 gallons in it now.
• The gauge shows that the tank is full now.
So I need help in figuring out what my capacity actually is. I thought I was supposed to have 120 gallons fresh water capacity. Do you know if the fresh water is split into two tanks?
The only explanation I can think of is that either:
(A) There are two 60 gallon tanks but the drain valve only drained one of them. The fresh water gauge was correct when it read 2/3 full after I had emptied only one of the tanks. (The gauge reads in thirds, so there’s no way to show when it is half full.)
(B) I only have 60 gallons capacity and the valve really did actually empty the whole thing. And the fresh water gauge is broken.
I just filled the water for a trip this weekend, so I don’t want to empty it again (plus it takes forever). The next thing I’ll try after the trip is to empty the tank again and then turn on all the faucets and see if anything pumps out.
In the meantime, could you talk to your tech who installed the fresh water drain and ask him if he saw one tank or two and whether this valve should empty both of them or not? Or is it possible that there is a blockage preventing one of the two tanks from filling?