| [GMCnet] Broken black tank valve [message #195585] |
Mon, 14 January 2013 13:47  |
Richard Brown
Messages: 281
Registered: May 2009
Karma: 1
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My black tank valve is broken. The rod seems to have become detached from
the blade. Has anyone figured out a way to open it without wearing the
contents? I plan to leave it open & glue in a new valve downstream.
Richard & Carol Brown
1974 Eleganza SE
1174 Hickory Hills Dr.
Murchison, Tx. 75778
(903)469-3197
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Richard & Carol Brown
1974 Eleganza SE
1174 Hickory Hills Dr.
Murchison, TX. 75778
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| Re: [GMCnet] Broken black tank valve [message #195592 is a reply to message #195585] |
Tue, 15 January 2013 08:35  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Richard Brown wrote on Mon, 14 January 2013 14:47 |
My black tank valve is broken. The rod seems to have become detached from the blade. Has anyone figured out a way to open it without wearing the contents? I plan to leave it open & glue in a new valve downstream.
Richard & Carol Brown
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Richard,
No
Matt
Discussion about your plan.
The Thetford valve was never designed to be all that good with the blade open. Actually, it was never designed all that well. (Sorry Frank, that is an opinion shared by a number of the engineers that worked for you.) If left open, with liquid backed up into the valve, you are then counting on the body gasket and the stem seal to keep it tight. Any side load on the plumbing may cause the body seal to breach and if the rod comes out of its hole, you have a 1/4" leak. Fortunately, the system as originally installed supports the pipe at the valve very well.
Unfortunately, if your coach is old enough to have the metal and plastic valve, it is no longer available at all. If you replace it with the all plastic valve (08709), you will find you have to cut new clearance in the frame just aft.
To empty the existing tank, hunt up a marina that has a "Pump Out" station. I suspect that the local lakes may have these. You will have to buy some fittings to attach to their hose and enough 2" pipe to reach into the tank through the toilet valve. Then you can suck the tank to very near empty. A couple of flushes and it should be less than really nasty. With that done, you could probably loosen screws and get it open enough to push the blade. (This last bit is conjecture on my part.)
For the short term, there is available hardware to put a new valve to put a valve on the end of the dump pipe.
By the by, blades may be available from Thetford. If it is be ready for it to not be a fast delivery. I found out last year that the hold all orders for two days before shipping. I may also have a used blade out in my Thetford valve parts collection. I will look later on today.
Matt - Again
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Broken black tank valve [message #195596 is a reply to message #195585] |
Tue, 15 January 2013 09:30 |
Richard Brown
Messages: 281
Registered: May 2009
Karma: 1
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Senior Member |
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I had an idea that I plan to try to open the valve. I plan on drilling a
small hole in the valve body 180° from the actuating rod & using a rod
that's a snug fit in the hole to push the blade open leaving the rod in the
hole until the black water is removed. Once the tank is empty I'll use a
short self-tapping screw with a rubber washer to seal the hole. I also plan
on removing the actuating rod & sealing that hole as well. We live in the
coach & it is on blocks right now so it's hard to get under. I saw those
valves with the hose type connections & am considering them. I empty the
black tank with a Shur-flo macerator & pump to a septic tank. All I'm
waiting on now is a change in the weather since we have freezing rain now &
it's below freezing here.
--
Richard & Carol Brown
1974 Eleganza SE
1174 Hickory Hills Dr.
Murchison, Tx. 75778
(903)469-3197
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Richard & Carol Brown
1974 Eleganza SE
1174 Hickory Hills Dr.
Murchison, TX. 75778
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| Re: [GMCnet] Broken black tank valve [message #195639 is a reply to message #195585] |
Tue, 15 January 2013 23:53 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Richard:
Here are pictures of that Valve you have.
http://www.gmcmhphotos.com/photos/thetford-black-tank-valve/p47174-thetford-valve-08.html
Seeing it apart can give you a better idea of what you may need to do.
a couple more ideas
1 - Maybe a little pressure and wiggling on the shaft with a vise grip mounted on the external end will re-engage the shaft into the tabs of the slide plate. It might be easier if you remove the small plate on the end and remove the 0-ring and sleeve to give the shaft some wiggle room.
2 - A small hole (1/8") and a punch in the downstream side housing aligned with the slide plate tabs in the slot area may also help you snap the shaft into tabs in the slide. There is no effluent on the downstream side and will not spill on you while trying to re-engage the shaft. A 1/8" hole is easy to seal with a 2 part epoxy once the sewage has been drained, and very little will spill into a bucket under the hole while the effluent flows.
3 - I guess if the tabs are broken, then you might to use an 1/8" hole in the opposite end of the shaft as you have suggested. I would also make sure you put a slot in the end of the 1/8" rodthat you would use to push the slide. While the rod is in the hole very little effluent should come out. You will see that a screw is in that spot and that might be useful when you need to seal it up again. ( A short rubber or plastic rod inserted and then pinched with the screw.
Best regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: [GMCnet] Broken black tank valve [message #195677 is a reply to message #195639] |
Wed, 16 January 2013 10:11 |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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I may have related this experience here before. If not I am sure it was posted on our blog.
Coming back from Oregon during a hot September we stopped for a couple of days on the California side RV park across from Parker, Az. I wanted to pay for the electric as it was 100 plus outside.
After parking I hit the 12 volt switch on our electric gate at the rear of the back tank. I heard it moving. Flipped the switch on the maserator, nothing pumping, just the motor running. Several folks had gathered to talk with me about the GMC and to pet our aging dog. Ever noticed how folks seem to gather when you are trying to dump the GMC? I fooled around for 30 minutes and just could not figure out what the problem was. I hit the 12 volt gate switch several times and I could hear it working. So, since I have a straight 3 inch pipe, coming out under the rear of the coach, thought I would hook the new hose on that. Must be a problem with maserator. Closed the gates, I have a manual gate at end of the 3 inch, and hooked hose on. Opened both gates, nothing.
I have several folks standing back near the Colorado River talking to me but not getting too close. It is hot and I am losing what little patience I was born with. I jerked the hose off, with both gates open, nothing. I got a flashlight and found that the 12 volt gate at the opening of black tank had pulled the rod out of the gate. Gate stuck shut.
Well, I sit there thinking about this while several old farts are offering opinions, but keeping their distance. I got up and went into the GMC while Teri visited with these guys. Came out with a 3 foot crowbar, "this will open it up". You should have seen all those guys take off. I stuck that crowbar up in there and pryed the gate open while Teri held the 3 inch hose, ready to pop on as soon as the enema giving crowbar came out.
Worked like a top. I am glad I have a simple setup with the 3 inch coming straight back and the maserator off to the side.
Great way to get rid of unwanted guests. Left the gate open til we got home and I fixed it in our driveway with no "visitors"
If you use your coach a lot, similar things are going to happen. Be prepared and keep things simple. Makes life stay good.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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| Re: [GMCnet] Broken black tank valve [message #195681 is a reply to message #195585] |
Wed, 16 January 2013 10:35 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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Senior Member |
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I had a similar situation the first time I tried to dump (before I'd even put anything in the black water tank, though the PO had "left some presents" in there....) 
I had clicked on the macerator for a second or two to make sure it ran (and it did, just fine). But when I opened the black water tank (manual slide vane valve) and hit the macerator switch, it groaned for about one second and stopped, then blew the self-resetting breaker. Aaaarghhh... Visions of having to hook up the 3" pipe with the valve "pre-loaded" in the 100+ degree heat at the dump station filled my head. The scene where Robin Williams first hooked up his dump pipe in the movie 'RV' came to mind...
Fortunately, the nice engineer(s) who designed my macerator was smart enough to put a large screwdriver slot in the motor shaft that protrudes from the rear of the macerator. So I just stuck a big ol' screwdriver on the slot, gave it a mighty twist, and felt something (don't even want to think about WHAT...) break loose. After that the macerator ran like a bandit. Whew!
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: [GMCnet] Broken black tank valve [message #195685 is a reply to message #195585] |
Wed, 16 January 2013 10:49 |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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Senior Member |
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Yep, I have used that slot a few times. I am probably the only GMCer that carries a spare maserator, and parts. But, I have replaced a few times. All quick disconnect, 5 minute job. Keeps things flowing.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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