blackwater waste valve seal question

[rlw999]

My blackwater valve is leaking around the shaft. Replacing it seems relatively straightforward but I've never done this before and have a question about the valve seals.

The seals have an inner lip, does that inner lip face inwards toward the valve (which is how it was packaged):





Or does it face outwards toward the pipe:



It will probably be obvious when I take off the old one and I see how the existing seals are oriented, but I'd like to find out before I take out the old one in case the seals fall off or are different.

This is probably a related question, but when the valve is closed, there's a small gap along the edges of the blade that would let water through -- are the seals supposed to press against the blade seal it? (I guess that would answer my question about orientation if this is the case, since that inner seal lip would face toward the valve). At first I thought it was a manufacturing defect, but I ordered 2 valves and they are the same, and I've seen some product pictures online that have that same gap.



I figured there'd be some diagram or something in the instructions, but the entire set of instructions that came with the valve is:


* Remove old valve and seals
* Place new seals over the lip of existing flanged fittings
* insert new valve being careful not to dislodge seals
* Tighten nuts and bolts provided



And finally, I have one last question, is there any value in coating the seals and/or blade with vaseline or silicone grease? I've seen both recommended in various places online, but the valve instructions don't say anything about it.

[rlw999]

Thanks everyone for your help.

As I'd hoped, it was obvious which way to orient the seals when I took the old one out - as everyone here said, it's the way shown in my first photo -- with that inner lip facing inwards toward the valve.

This one was super easy and no mess at all, my blackwater tank has 2 valves, one near the tank, and this one by the drain outlet. I installed a blackwater tank flush system too, so after I flush out the tank well I'll swap out that other one which has become very hard to open. And I'll take @Horsedoc's advice and use my leveling blocks to angle the RV to keep residual liquid from dripping out.

The one piece of advice I didn't follow here was replacing the bolts with stainless steel - the current bolts weren't very rusty and were easy to get off. After tightening the new screws, I did coat the nut end of the threads with some grease, though I'm not sure that's really going to make a difference after a few years and I need to do this again unless I remember to do it regularly.

[Veebyes]

The DW & I changed our black tank valve last week. Never a pleasant job made more unpleasant by difficulty of access & extremely little room to separate flanges to get valve in without dislodging the seals.

In my application the seals are placed on the pipe flanges, separate, insert valve, bolt together.

Advice. The chances are that the bolts are severely rusted. Avoid this problem in the future by getting a set of stainless steel bolts & stainless nuts with the nylon insert.

[Horsedoc]

Suggest that when you get ready to do the replacement park with the left side higher than the right so that any residual liquid flows away from the valve and not out on your hands and work area. ( Some things are just nasty no matter how much soap and water is added before the work is done)

[ksg5000]

Last time I had this issue the entire gate valve didn't cost much more than the gasket ... many just replace the valve. Just a thought.

[jdc1]

Chemicals are a waste of money. A little bit of dish soap, if anything, is all that is needed.

[smarty]

the first pic is the correct alignment of the gasket

[mobeewan]

Couple of videos:

waste valve replacement / maintenance

Waste valve replacement / maintenance 2

[rlw999]

Oasisbob wrote:
Sorry I cannot answer your question. May I ask if you use chemicals in the tank? How old? A friend just replaced his black tank valve after less thyan one year. My rig is 20 years old and I have never had a leak nor have I ever used chemicals. Just curious

I do use "Happy Camper" tank chemical, but this RV is 4 years old and I've only had it for a couple months and I have no idea what the previous owners used. Only one of the 2 blackwater valves is leaking, the one that's right next to the tank seems fine and that one is exposed to the tank contents full time, so I don't think this is related to toilet chemicals. That other one is pretty hard to pull, so I'll probably swap that one out too after I see how this one goes.

[Oasisbob]

Sorry I cannot answer your question. May I ask if you use chemicals in the tank? How old? A friend just replaced his black tank valve after less thyan one year. My rig is 20 years old and I have never had a leak nor have I ever used chemicals. Just curious