Holding tanks don't drain completely

[Dejones57]

I always give my tanks plenty of time to drain but inevitably when I use the trailer next about half a gallon of what I can only hope is grey water spews out when I take the cap off of the drain pipe to attach the sewer hose. No smell so it probably is grey but still....normal or not?

[Canonman]

What model trailer?? Our Cougar has a separate grey tank for the galley. It's a long way from the tank valve to the terminal valve where the dump hose is connected. If the rear of the Cougar is lower than the terminal valve some liquid will remain in the pipe.
Same will hold true for the grey and black tanks but the issue is side to side.
Here's the quick fix we use to eliminate the "surprise" when you open the cap on the main drain.
http://www.campingworld.com/shopping/item/twist-on-valve/27868

[fixn2gocamp]

Are you closing your gray T valve when you are done draining it? Not pulling it open until you have the sewer hose connected at the next stop? It may just be what's "leftover" or shaken loose from traveling...? But I don't think you would encounter it if you have your T valve closed. Been doing this for 8 years, notice a little run when I connect and pull the valve, but I don't think its a half gallon unless something was run into the grey tank from the camper. Somebody washed their hands, or something similiar...:confused:

[JRTJH]

I always give my tanks plenty of time to drain but inevitably when I use the trailer next about half a gallon of what I can only hope is grey water spews out when I take the cap off of the drain pipe to attach the sewer hose. No smell so it probably is grey but still....normal or not?

That's why most of us install one of these on the end of the sewer connection and put the cap back on. You simply remove the cap that you already have, twist the valve on in its place and then reinstall the cap on the valve. No modifications needed and it takes "literally one minute" to install. It's an extra valve to open and close, but it's also a very valuable "added insurance" against that "half gallon of stuff" that flows out when you remove the cap. I don't know very many "multi-year RV'ers" who don't use the "terminal valve" and a end cap with a garden hose connection. Once you've been "deluged with liquid crap" one time, you'll make it a priority !!!

Both of these is less than $30 and is "money well spent" !!!

[Johnny's Journey]

Once you've been "deluged with liquid crap" one time, you'll make it a priority !!!Then this is common ? I was going to rebuild the "new" dump valve on my new travel trailer because I thought it wasn't sealing correctly since my other travel trailer had one that was as water tight as a frogs ___, well you get the idea.

[chuckster57]

Then this is common ? I was going to rebuild the "new" dump valve on my new travel trailer because I thought it wasn't sealing correctly since my other travel trailer had one that was as water tight as a frogs ___, well you get the idea.


Common? It shouldn't be and isn't on my fiver. The cause can be waste water left in the drain lines due to angle of trailer, or a leaking blade valve. Now that pretty much all trailers have a sealed belly, servicing the blade valves is more difficult and the additional valve at the termination fitting is an easy fix.

[Dave W]

No, not a common thing but as others above have mentioned it does happen. I straighten the hump in the center induced by a too short bracket and resloped the 1-1/2" kitchen gray tank drain line to the dump and it 'fixed' ours, But with that said, I still have that secondary valve, just in case plus a garden hose drain cap that probably has never been used. And occasionally the main tank gate valve leaks as well, usually by having something foreign stuck in the seal. Even the gray tank valves. If that's the case, it may eventually flush out .... or not. Then you dig in and manually clean or replace it which is never fun. Or just let it seep.

[Johnny's Journey]

Then there is such a thing as blade leakage. Thank you.

[chuckster57]

Then there is such a thing as blade leakage. Thank you.

Sure is. Hate it when the factory uses too much glue and it runs into the channel where the blade runs, but at least it's CLEAN water.

[Johnny's Journey]

Sure is. Hate it when the factory uses too much glue and it runs into the channel where the blade runs, but at least it's CLEAN water.Sweet an actual cause that gives some insight to my issue. I'm not afraid of get dirty or of tricky to assemble components.