Saturday, December 10, 2022


Ask Dave: Fresh water drain valve trickles, doesn’t drain


Dear Dave,
I follow the owner’s manual instructions to drain the fresh water tank at the end of a trip. I open both valves in the hold below the bathroom, but I get only a few minutes of drainage. Also, I have tried when changing the fill valve to fill the tank rather than normal use and or opening a faucet. Nothing helps. The only way I can drain the tank is to put the fill valve in normal operation and run the pump. The water then drains from both drain valves. But without the pump running, I cannot drain the tank. Please advise. —Ted, 2010 Winnebago Adventurer 35P

Dear Ted,
According to the owner’s manual I found on the Winnebago site, there are two different fresh water drain valves. One is for the water lines that are located in the compartment just behind the entrance door. The actual fresh water tank drain is a “T” handle with a cable to the actual drain valve and is located in the compartment rear of the right-hand rear wheel lip. This is a photo of one in a 2010 Adventurer 38N, which is located just to the right of the entrance door.

Here is the floor plan layout of your 35P:

So, according to this, the bathroom is directly next to the entrance door so the compartment underneath this, which you referenced, is the compartment that has the water lines drain valve. According to the 3D diagram available on the Winnebago Owner’s Resource page, the valves for the lines look like this.

A diagram of the fresh water drain valve systemA diagram of the fresh water drain valve system

When you dump the fresh water tank in just about any plumbing situation there is still water in all the lines. These valves are designed to open the drain and let the onboard pump drain out the lines.

The owner’s manual stated the fresh water tank drain valve was located on the right side, which would be the passenger side, as they typically described left and right as it would be sitting in the driver’s seat looking forward. It went on to state it was in the compartment rear of the rear wheel lip, which would be the back duals and the compartment under the bed slide.

So my guess is you are opening the line drain valves and not the “T” handle valve that goes to the fresh water tank.

 You might also enjoy this from Dave 

 Quick RV Tech Tip
There’s still some water in the fresh water tank when I winterize. Is that okay?

Dear Dave, 
I *thought* I fully drained my fresh water tank when winterizing. However, I realized the drain valve comes off the side of the tank and leaves about 1.5 inches of water in the bottom. Even tilting the trailer as far as possible still leaves about 1/2 to 3/4 inch of water in the tank. Is this amount of water safe to allow it to freeze? I thoroughly blow out the rest of the system and run the pump dry, and would prefer to only use RV antifreeze in the waste traps. —Jim, 2022 Gulf Stream 189DD travel trailer

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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16 days ago

Its good to have a Winnebago expert with us & share his information! Crazy how & where the drain valve is & you have to pull a “T” handle that goes to the tank drain!

Bob p
16 days ago

Sounds like a visit to the owners manual may have some surprise answers to questions.