Community Forums

MichaelJude · 12-29-2018, 09:29 AM

My gray tank drains very slowly. Does anyone know how to fix this?

Jake21 · 12-29-2018, 01:44 PM

How is the positioning of the sewer connection? If there is a rise in the connection where you hook your hose up to it, then flow will be slowed.

Waiter21 · 12-29-2018, 01:52 PM

My Sourthwind also drains slow. I need to look at the vent..

Bob_C · 12-29-2018, 02:03 PM

Are you sure the gate is opening wide?.....Cable or rod activated?

EdInArk · 12-29-2018, 02:52 PM

How slow? Our gray tank drains more slowly than our black tank, but then, the drain tube is much larger on the black tank. I drain the black, which takes several seconds, then I drain the gray and go about my other business. When I'm back it's finished.

MichaelJude · 12-30-2018, 05:18 AM

It’s a rod valve. Hose is clear and level. Valve seems to be opening fully, because the initial flush is strong and fast, but then the flow slows down to a trickle after a minute or two, and then the flow gets very low and it takes a many minutes to finish draining fully.

speed racer · 12-30-2018, 05:37 AM

It drains slow because it is only a 2 inch pipe and a 40 gallon tank. The black tank drains faster because it is a 4 inch pipe. It helps to raise the front of the MH a little.

EdInArk · 12-30-2018, 07:50 AM

Quote:

Originally Posted by MichaelJude

It’s a rod valve. Hose is clear and level. Valve seems to be opening fully, because the initial flush is strong and fast, but then the flow slows down to a trickle after a minute or two, and then the flow gets very low and it takes a many minutes to finish draining fully.

Quote:

Originally Posted by speed racer

It drains slow because it is only a 2 inch pipe and a 40 gallon tank. The black tank drains faster because it is a 4 inch pipe. It helps to raise the front of the MH a little.

That seems normal to me too. The more volume you have in the gray tank the more pressure you have pushing it out. When it the level gets down less than the diameter of the pipe it slows down and will trickle for several minutes. Ours drains from the left (driver side) of the tank, so I can raise the right and it'll come on out. But I just drain the tanks first and do the rest of my stuff while the gray's draining. By the time I've got electric and water disconnected, it's finished. If it's still a slow trickle I don't care. There's not enough in it to worry about.

sbleiweiss · 12-30-2018, 07:54 AM

Doesn't seem normal to me. Neither of ours have done that. I'd be looking to make sure the vents are clear.

EdInArk · 12-30-2018, 08:04 AM

Quote:

Originally Posted by sbleiweiss

Doesn't seem normal to me. Neither of ours have done that. I'd be looking to make sure the vents are clear.

Michael has a National Seabreeze LX.

Ours drains from the side at the bottom of a flat tank, so as the level falls below the height of the pipe it keeps slowing until is barely a trickle. If the tank were shaped to taper toward the drain it'd work better.

Richard S. · 12-30-2018, 08:17 AM

Just for reference the type of valve, is a GATE VALVE and most National RV's gray tanks drain slow.

docj · 12-30-2018, 08:32 AM

I'm surprised that none of the previous posts have mentioned that gray tanks can develop deposits of "crud" that can eventually block the ~2" drain line. The crud can be soap scum, hair, food particles, etc. Worst of all, calcium carbonate deposits from hard water can also develop over time. I know because we had this problem a few years ago.

I found a couple of ways to deal with the problem. There is a franchised company known as All Pro Water Flow, nationwide network of holding tank cleaning companies that specializes in cleaning black and gray tanks. They use specially designed pressure washing tools to get inside the tanks. It's amazing how much stuff can come out of even a gray tank.

Alternatively, if you think the problem is mostly in and around the valve itself, you can use one of these things https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1 to force water back inside the tank in the hopes that it will dislodge the clog. This valve is different from most other "reverse flush" units because it has an external gate valve which, when closed, forces water back into the tank. I use it for a few minutes to put water in and then I drain it back out. Usually if there is a clog it will break up and come out in pieces.

Lastly, with limited success, I have tried pouring liquid dishwasher detergent (dishwasher, not dish detergent!) into the gray tank, filling it up with water and then draining it after a few hours. A lot of the crud in the gray tank is the sort of stuff dishwasher detergent is designed to deal with.

Joel (AKA docj)

GREGORYJ · 12-30-2018, 08:46 AM

Our 05 Dolphin and current 08 Dolphin grey tanks also drain slowly, especially near the end of draining, that is it just keeps slowly tricking out. It seems to be normal, the tank is large and shallow, 8 feet x maybe 4 feet x 9 inches in height. Then there maybe be a length of the 2" pipe the grey water has to run thru before it gets to the drain valve. When it gets down to the last 1/2" of grey water in the tank, it's not going the "rush" out. I often tip the RV towards the drain side with the rear right leveler to try and speed up the draining. See image for 04 Dolphin tanks and drain plumbing below:

gvette85 · 12-30-2018, 02:30 PM

Our 04 Dolphin drains similarly.When the valve is first opened it rushes out but as it nears empty it slows to a trickle for several minutes.Previous owner told me this is normal.