Black Tank Dump Valve

[CarnationSailor]

When I dump a full black tank, the valve opens very easy, no problem. I flush the tank for 5 to 10 minutes, then I close the valve for 5 minutes to let it partially fill. When I then pull the handle to open the valve again, it is so difficult that I almost cannot open it. Been this way for a couple of years, and now I thought I might do something about it.

I put tank valve lubricant in the tank periodically, but that doesn't seem to make any difference. Any ideas why full it is a piece of cake to open, and after flushing and partially filling, you almost need a gorilla to open it.

[CarnationSailor]

Update: The difficult operation is not related to flushing the tank or pressure building up in the tank. I dumped the black tank and as usual the valve was easy to open. While dumping and for a total of 10 minutes, I ran water in thru the flush port. Then I closed the valve and tried to re-open it. It was very hard to operate.

I think I am going to try the valve lubricant that you put in the tank one more time, and then, if that doesn't work, probably have the valve replaced.

[RLS7201]

IAMICHABOD wrote:
I found that lubricating it during a dump as in this video works.

I have used this method for many years to lubricate my valves and have had no problems with them at all.

This Video will show how to do it

I did the same only different. I drilled, tapped and screwed in grease zerks. Then lubed with chassis grease. NO! the seals are NOT rubber.

Richard

[Durb]

Lynnmor wrote:

CarnationSailor wrote:


If I recall correctly, the roof top vent cap is attached to the vent pipe with screws. So it seems unlikely that the pipe slipped down; however, if it did, then the vent cap should be missing. At any rate, I'll check out this possibility.

For some information Google: rv vent pipe slipping

As a test, turn off the black tank rinse then flush the toilet which will relieve any tank pressure. Then, try the valve.

[Lynnmor]

CarnationSailor wrote:


If I recall correctly, the roof top vent cap is attached to the vent pipe with screws. So it seems unlikely that the pipe slipped down; however, if it did, then the vent cap should be missing. At any rate, I'll check out this possibility.

For some information Google: rv vent pipe slipping

[CarnationSailor]

IAMICHABOD wrote:
I found that lubricating it during a dump as in this video works.

I have used this method for many years to lubricate my valves and have had no problems with them at all.

This Video will show how to do it

Looks like a good solution for sure - if your dump valves are exposed and easy to get to. I would have to either drop the coroplast or cut a hole in it, and I'm not ready to go there yet.

[CarnationSailor]

Lynnmor wrote:

Durb wrote:
Do you turn off the water to the black tank rinse before opening the valve? Could be the incoming water is building pressure inside the tank and binding the valve.

Good thought. The tank has a vent thru the roof and can only build pressure if that vent is blocked. What can happen is that the vent pipe slipped down into the tank and is now under water, or even worse, resting on the bottom.

If I recall correctly, the roof top vent cap is attached to the vent pipe with screws. So it seems unlikely that the pipe slipped down; however, if it did, then the vent cap should be missing. At any rate, I'll check out this possibility.

[CarnationSailor]

Durb wrote:
Do you turn off the water to the black tank rinse before opening the valve? Could be the incoming water is building pressure inside the tank and binding the valve.

I think if this was happening, the vent pipe would also have to be mostly blocked, but not so much that normal usage builds pressure. I could test this by waiting 30 minutes or so after partially filling tank to give it time to bleed off. If it works easily after giving it time to bleed off, then I think this might prove your theory.

[jdc1]

Add liquid detergent to the tank occasionally.

[Lynnmor]

Durb wrote:
Do you turn off the water to the black tank rinse before opening the valve? Could be the incoming water is building pressure inside the tank and binding the valve.

Good thought. The tank has a vent thru the roof and can only build pressure if that vent is blocked. What can happen is that the vent pipe slipped down into the tank and is now under water, or even worse, resting on the bottom.

[Durb]

Do you turn off the water to the black tank rinse before opening the valve? Could be the incoming water is building pressure inside the tank and binding the valve.

[IAMICHABOD]

I found that lubricating it during a dump as in this video works.

I have used this method for many years to lubricate my valves and have had no problems with them at all.

This Video will show how to do it

[LadyRVer]

Might try spraying handle/metal rod with silicone. Or probably just need to replace. I did my tank, took me about 3 hours.. but I got it done.

[CA_Traveler]

Something in the seal dries out over time and then swells with usage? Regardless why not just replace the valve and be done with it?