3 inch grey water drain?

Thanks for all the answers so far. When draining the grey tank, it comes out at a VERY slow rate. We have a clear elbow,so we can see the the rate of flow. We are not trying to get the last drop out of it,its slow from the start. I thought they must have left a cut out disc in it also,but the tank itself is molded as is the outlet on the tank ,so nothing to cut out. Its raining here today so I'll wait until tomorrow to keep looking. So far the drain pipe from the end where the drain hose connects is wide open as is the slide valve. I'll next try to run water down the roof vent and see what happens as long as everything is apart. Again Thanks for all the help on this

Please post back and let us know what you found and or how you resolved the problem....I like to learn.

If the tank vent is clear, sounds like something is blocking the pipe between the tank and the 1-1/2 inch dump valve. You may need to pull the valve and see if something is blocking flow against the valve. While the valve is out check the pipe on both sides for blockage just in case.

1Longbow wrote:
I thought they must have left a cut out disc in it also,but the tank itself is molded as is the outlet on the tank ,so nothing to cut out.

While the outlet may be molded, the inlet (where the sinks drain into the tank) may not be. So there could still be a cutout disc in the tank.

When I bought my Winnebago new in 2008 I had a similar draining problem. After a couple of months and lots of frustration the problem fixed itself.....the disc that had fallen into the tank during construction worked it's way out during dumping. No more draining problems since

I have a similar issue with my grey tank, but only when I use a Sewer Solution to dump at home slightly uphill into my septic tank inlet clean-out. Regular dump station? Done in seconds. My situation is clearly the outlet restriction of pumping through a 3/4" hose. From the sounds of it, there is something blocking the tank outlet upstream of the blade valve.

Well after spending all day ,under the rv and on top of the rv,I can find no blockage anywhere!
I found that if I tilt the trailer ,with the front jack,the tank drains faster. So my only guess is the design of the grey tank or the angle that its mounted to the under carriage. I'm kinds dumb founded at this point,but I guess it is what it is. Thank you very much for all your ideas,they were all very helpful---Thank you

Well ,I replaced all the grey water plumbing with 2 inch pipe,and while a 1/2 inch more may not sound like a lot ,the difference is amazing!I filled the grey water tank ,opens the valve and it flowed like who goosed the moose, Thanks for all your suggestions