If you own an older RV there is a good chance you will experience a problem with a non-draining holding tank at some point.
There are two causes for a non-draining holding tank:
- A clogged tank.
- A broken drain valve
It’s almost always the black water tank that gets clogged to the point it won’t drain properly but in extreme circumstances a gray water tank may clog too.
But it is not clogged tanks I want to cover here.
In this tip I want to talk about dealing with a broken waste valve. While some of what I cover here will apply to cable-pull and electric valves they have additional diagnostic procedures I will not cover.
When a drain valve gets old and clogged with ‘stuff’ it can get hard to pull the gate open. This extra effort and the rapid stop at the end of travel once you do get the gate to open puts stress on the connection of the pull rod to the valve blade. Overtime, the extra stress can, and often does, break.
Once the rod separates from the gate there is only one way to drain the tank. It’s a nasty procedure but you can minimize the hassle and the mess by being prepared.
Before I go further, I need to say what will be obvious to most. This procedure will take some time. Out of courtesy to your fellow RVers the work should not be attempted at a busy public dump station. It should be performed at a campsite with hookups or a less busy dump station. You should also see my post on How to Replace a RV Waste Valve.
What you will need:
- A saw that will cut plastic
- Long needle nose pliers
- A replacement waste valve on hand.
- RV sewer hose
- A bucket or pan that will fit under the drain valve
- Some rags
- A pair of rubber/latex gloves is a good idea
Procedure to dump the tank:
- Connect Your RV sewer hose to a dump station
- Extend the pull rod all the way open
- Use the saw to cut through the valve body at about the mid section.
- Place bucket or pan under valve
- Use needle nose pliers to reach inside the valve body and grasp the valve gate.
- Pull gate out to allow tank to drain through the hose
- Use rags to minimize waste leaking from cut.
- Flush tank until water rums clear
- Let tank drain completely
- Replace old valve
It should be obvious that preventing the need to perform this procedure by replacing hard-to-open valves BEFORE they break is preferable. You get to pick the time and place and avoid a lot of the mess and hassle.