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Black Tank Valve Won't Close


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Well don't you wish you could be me? I get to work on my sewer valve...  So what happens when these Valterra valves fail open? Does the valve plate go past center? It's 12 yrs old. This is the 2nd time it's hung up in 3 yrs.  Should I replace the valve?

Edited by Don SC
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Our Valterra valves are about 22 years old and still function . My black tank valve does leak a small amount , so I installed a third and final valve . 

Anyway , when the valves start feeling 'stiff' , I spray lube and probably more than enough . Some times it doesn't last a long time and others it seems to be fine a lot longer . 

Back flushing seems to help alot . 

With the third valve in place and open , I first dump the black . Then close the third and open the grey and let it back flow into the black until something close to equal . Then pull the third for a final drain . 

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Most common is some trash stuck in the valve seat. We had it happen. Did a extra intense tank flushing, including a 24 hour soak with a bottle of Dawn and Calgon,followed by another full tank waterflush.

Took the valve apart and cleaned it up. it was more or less clean after the flushes. Lubed the stem with some silicone grease. Put back together and it's worked well ever since. Only four long bolts holding the valve in/and together. Not count flush time maybe a 2 hour job.

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3 hours ago, Don SC said:

So what happens when these Valterra valves fail open? Does the valve plate go past center?

I have never seen one fail open but if you must experience a dump valve failure, open is easier to deal with. I would probably replace a valve that did that and it really isn't a bad job with the tanks empty. You can get replacements from Amazon and they have several brands of them. As to why it happened, it is difficult to guess but if you pull it out and take it apart you may be able to figure that out. There is a Valterra valve kit to replace just the working parts or you can get the entire valve. I do believe that any of the valves will interchange, but have only compared 2 different brands do be careful of that. 

On the maintenance side of things, it is a good idea to lubricate those valves occasionally and I have always put a quart of mineral oil into my waste tanks immediately after emptying them once or twice each year to lubricate the blade. After letting it sit for 10 minutes or so, I then quickly open and close it as rapidly as possible in order to coat the blade before using it. Lubrication can also be done by drilling a hole and installing a plug into the housing and then using some silicone based lubricant into the housing. See this video.

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I forgot to mention that it's a cable operated valve. I've always tried to keep it clean and lubed. Valve is out now and I took it apart and siliconed it but the cable is stuck. The valve plate works ok. I thought it rotated until I got a look at it. Then I saw that it is a slider.   8 ft long cable.I had to remove some of the underbelly fabric to access. It turned out not to be a Valterra, but a Plymouth Bristol.  I looked for the brand online but only came up with a LaSalle Bristol. It's made differently than mine tho. So I worked my valve over pretty good and still ended up same as before, . stuck wire inside that 8 ft. long cable.. Well I'm at home,  not travelling, so I'll continue tomorrow with this thing....

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8 hours ago, Don SC said:

It turned out not to be a Valterra, but a Plymouth Bristol.  I looked for the brand online but only came up with a LaSalle Bristol.

I did a lot of searching and can only find LaSalle Bristol by searching for either parts or manufacturers. I also found replacement cables for the LaSalle Bristol waste valves so you may want to take a look at those. I also reached out to one of the members who is a mobile RV tech so perhaps he may be able to help.  Keep us posted what progress you make. It may be possible to free up the present cable using spray lubricants or possibly a product like Break Free. I think that I would consider replacement of the cable even so, just to be sure you never have a situation where it seizes up with the tank full. 

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I sure do appreciate all you’ve done Kirk. A knife valve. I knew that a long time ago… when I was a young guy and could remember stuff.

I’ve let it sit overnight with penetrant. It’s gonna get replaced with a new cable .

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One big hint, like the saying goes, crap flows downhill. Always lower the side of the trailer AWAY from the dump valve when you remove it to prevent you from having a surprise when you remove the valve. By making that side of the trailer 6 to 8 inches lower, you prevent something like that from happening.

 

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  So thinking about what I have seen before on a valve that will not close.

 

  I have seen a few through the years doing rv repair that would not close. One thing I remember was the cable to work the valves was stranded. Not solid. Apparently one strand broke and was keeping the valve from operating properly. It would grab the inside of the case.

  So I always used a cable assembly that had a solid wire in it.

 

  Hope this helps,   Vern in a dirty T shirt.  Yes I have had you know what up my T-shirt in the armpit.

 

 

 

Edited by Wrknrvr
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    Since I am talking about dealing with a waste valve, I will share some tricks to help the situation.

  First thing is I’d you remove all 4 bolts, then rotate the valve 45 degrees. Now you can install 2 long bolts through the flanges. Use the 2longer bolts that came with the valve kit. While u are doing this put 2 nuts on the bolts , between the flanges. Now if you work the nuts away from each other slowly,it will open the space between the flanges. So this should give you space to remove and replace the valves.

 

note   Do not push the flanges to far as the flange corner could brake off. It’s not my fault if it happens?

 

  The next thing to do before any installation is to clean both flanges really good. Then lube all surfaces with dielectric grease. Available at automotive stores. It is not silicone seal. It is pure silicone.

  Put the silicone on the new valve or old valve, the seals on both sides need to be lubed with silicone also before installation. And lube the blade of the valve. This should make the installation much easier and will keep stuff from sticking to the valve.

 

 Vern,     that threw that really dirty T-shirt away.

Edited by Wrknrvr
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New cable and seals ordered. The old cable is a single wire. I hope the new one is too. It didn’t say on etrailer.com

Wrknrvr , I heard an explanation of a plumber verses a pipe fitter one time… you put em both in a vat of cr-p , swing a shovel at their heads, and the plumber will duck…😹

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On 10/11/2021 at 8:13 PM, Don SC said:

I forgot to mention that it's a cable operated valve. I've always tried to keep it clean and lubed. Valve is out now and I took it apart and siliconed it but the cable is stuck. The valve plate works ok. I thought it rotated until I got a look at it. Then I saw that it is a slider.   8 ft long cable.I had to remove some of the underbelly fabric to access. It turned out not to be a Valterra, but a Plymouth Bristol.  I looked for the brand online but only came up with a LaSalle Bristol. It's made differently than mine tho. So I worked my valve over pretty good and still ended up same as before, . stuck wire inside that 8 ft. long cable.. Well I'm at home,  not travelling, so I'll continue tomorrow with this thing....

You answered what I was about to ask!

Before you decide to replace the valve - look for kinks in the cable (and the wire inside the casing).

Over time, *If* the cable developed slack - when you push or pull, a kink may result -  the valve doesn't open or close properly anymore.  When mfgrs decided the valves should be as close to the tank/s as possible, the factory installers may have included bends that "change" to "binds" - as they didn't care about keeping the cable as straight as possible.

Valves used to be easy to get at - usually easy to access somewhere along the 3" drain, no cable - just  via the "pull-handle" on the valve.  If your faulty valve is a PITA to access - and is in the "open" position, you can add another valve downstream to use it "old style".

Good luck,  not a fun job - even with an empty tank - if your valve is under the "belly" of the RV.  Been there, done that...😕

.

 

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7 hours ago, Pappy Yokum said:

Valves used to be easy to get at - usually easy to access somewhere along the 3" drain, no cable - just  via the "pull-handle" on the valve. 

For the same reasons I am no fan of the electric valves either. I have never been able to understand the reasoning for the locations chosen as dump valve in many of the newer RVs. I think that it is one more example of something that was simple and easy until the engineers got involved!  🙃

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