Replacing Thetford waste valves

[A W Warn]

Procrastinating caused me to have to deal with a stopped up black tank! It was an educational experience getting things flowing again. I will never ignore it again!

The drip I knew that was coming from the black tank has now turned into a trickle, leaving solids in the tank that would not go through the open valve. So here I am 700 miles away from home, and most of my tools, doing this crappy (literally) repair. This photo shows volume of the leak with the valve closed, about a quart every 15 minutes. That lets the liquids that accumulate each day seep out overnight!


There is not enough space to get my large self under the trailer, so I had to block up under the tires. I lifted the trailer 7 1/2".


I first cut out an 18" x 18" access, but realized that I could not easily get to the bolts and clamps on the gray tank, so I cut out another ~2" toward the rear (photo right). My Wiss snips would not do the job so I bought a cheap metal shear at Harbor Freight.


I picked up the tank adapters from ODM last fall, but did not get the valves since I did not know which model I should get.
After cutting the access I could see which type I needed. I ordered the valves online yesterday. ( waiting waiting)
I'll pickup new pipe and fittings today.

There is one more item to purchase, but I'm not sure what it is. Does anyone know what sealant was used originally where the tank adapter slips into the tank?

[A W Warn]

The Thetford valves arrive late Thursday afternoon. Friday morning I filled and dumped both tanks several times, Then I filled them with a bleach/water solution and let them set a while. I got started removing the old stuf just after noon on Friday. I decided to replace the hose adapter changing from the Thetford connector to the Valterra, so I had to make a trip to get it. I also made a run to the hardware when I discovered I picked up two cans of pipe cleaner, but no glue. I was done with install, cleanup, and putting away tools by 3:30.

It took a little over an hour to remove both valves and the old pipe. It took a little less than an hour to reinstall. I reused the original rubber connector since the newer ones are a little longer.

New material list:
2 - tank adapters
2 - Thetford waste valves - #08709
1 - 3 x 3 x 3 ABS combination fitting
1 - 3" ABS street el fitting (90 degree / quarter bend)
1 - 1' schedule 40 ABS pipe
1 - Valterra T1029-2 termination adapter
1 - 45 degree clear hose adapter
1 - pipe cleaner/primer
1 - glue (the multi use type for both ABS and PVC)
1 - tube Lexel caulk (instant waterproof type to seal tank adapters)

Total for new materials was ~$170, including shipping cost.
I reused the existing clamps and screws since they were all in good shape.



I still need to fabricate and install a metal access cover over the opening I cut in the tank pan. I'll get that accomplished after waiting a few days to make sure there are no leaks.

[jshotton]

I have a leak in both the gray and black tanks. The gray has 1 rusty corner on the pan. The black is coming from the top down the side. Do these sound like Thetford valve leaks? Are the tanks metal or plastic? I have a 2004 30' Classic.

[Wingeezer]

Watching this with interest in case I need to do the same!

A couple of questions if I may ........

(1) what type of metal "Shear" did you wind up using since the snips you had were not up to the job? Were they compound aviation snips or some kind of air nibbler or ?

(2) Since you are changing the outlet fitting to Valterra - something I am thinking about doing as Valterra stuff is way more available, was there a reason that you settled on going with replacement Thetford valves rather than Valterra?

(3) I'm not clear how the valves actually attach to the tanks having never seen them. I would have guessed there was a 3" pipe outlet stub on the tank and maybe a short 3" hose connetion to the valve, but from your write up I guess not so.

You mentioned having to buy "adapters" do they screw onto the tank, then a hose coupling to the valve? If so, were you not able to just use the ones already installed?


Many thanks again for posting this!

[crispyboy]

Wingeezer,
I have done this job but only changed the adapters and rebuilt the valves.

1.) Metal Sheer - Air shear is best for this job.
2.) Thetford valve - I reused the original Thetford valves but cheaped out and rebuilt them with a kit.
3.)Tank attachment - there is a 3" nipple on the tank. The adapter (black part next to the valve in AW Warns picture), gets slid into the tank nipple. Put some sealant on the adapter before sliding in tank. I think I used Vulkem or Sikoflex - don't remember for certain, but it looked like what the factory used. There is a large worm clamp (hose clamp) that goes on the tank nipple.
The Thetford valve gets bolted to the adapter.
The remainder of the black abs pipe is glued together.
Remember to get a piece of galvanized sheet metal (HVAC ductwork) to put over the hole cut in the pan. Fasten with very short screws. I think I used 1/2" screws and ground them down much shorter.
To get the trailer elevated high enough to work under I back it up onto some heavy duty Rhino ramps (oil change ramps) and put the tongue jack down to elevate the rear of the trailer.

[CRH]

I did the job a couple of years ago. I used electric shears from Harbor Freight.... Less than 40 bucks... I went to the recyclers and bought an old street sign to make a cover panel from.

[A W Warn]

Originally Posted by jshotton

I have a leak in both the gray and black tanks. The gray has 1 rusty corner on the pan. The black is coming from the top down the side. Do these sound like Thetford valve leaks? Are the tanks metal or plastic? I have a 2004 30' Classic.

I'm not sure what type of valve your 04 has. Tanks are plastic.
My 2000 Safari had Valterra valves, my 99 has Thetford valves.

[sheriff1]

Maybe I'm missing something, I just bought an auxiliary valve that goes on where the hose attaches. Grey and black valves still function withe the auxiliary as the final stop.

[A W Warn]

Originally Posted by Wingeezer

Watching this with interest in case I need to do the same!

A couple of questions if I may ........

(1) what type of metal "Shear" did you wind up using since the snips you had were not up to the job? Were they compound aviation snips or some kind of air nibbler or ?

(2) Since you are changing the outlet fitting to Valterra - something I am thinking about doing as Valterra stuff is way more available, was there a reason that you settled on going with replacement Thetford valves rather than Valterra?

(3) I'm not clear how the valves actually attach to the tanks having never seen them. I would have guessed there was a 3" pipe outlet stub on the tank and maybe a short 3" hose connetion to the valve, but from your write up I guess not so.

You mentioned having to buy "adapters" do they screw onto the tank, then a hose coupling to the valve? If so, were you not able to just use the ones already installed?


Many thanks again for posting this!

1. I started out using Wiss hand shears (aviation type) but had a difficult time with my arthritic hands. So I purchased electric nibbler shears from Harbor Freight. The same as CRH mentioned above for ~$40. Not a great tool, but it got the job done.

2. Valterra did not have a direct replacement valve with the offset extension rods that are required to extend the handles to the exterior on my trailer. (at least I could not find one)

3. The flanges of the old waste tank adapters were cracked around the bolts. 18 year old plastic looked bad. It only cost a few $ for new adapters, so it made sense to replace them. On my trailer the tank has a coupler built into the tank, though it will not receive 3" pipe. The waste tank adapter slips into the tank coupler. The slip joint is sealed with waterproof caulk and clamped with a heavy duty hose camp.
The adapter connects to the Thetford valve using 4 SS bolts. There is a rubber ring washer on the valve that compresses as the bolts are tightened. On my trailer the sewer pipe fitting glues directly onto the valve outlet.
This is the tank adapter I used:
http://odmrv.com/catalog/index.php?m...oducts_id=1092

There is a rubber coupling that connects the elbow fitting to the combination wye fitting. I originally thought this was for ease of installation. During the installation I realize this rubber coupling separates the tanks from stresses. The tanks have a lot of flex, between empty and full levels which could crack the plastic parts. Stresses while traveling could break the plastic parts. I am mentioning this because I have seen one installation where the coupler was eliminated.

[tinbender]

Subscribing

[A W Warn]

Originally Posted by sheriff1

Maybe I'm missing something, I just bought an auxiliary valve that goes on where the hose attaches. Grey and black valves still function withe the auxiliary as the final stop.

Many people do this. I thought about it, but did not like the way it would look. And I was afraid that it might catch on something, break, and let the leaked sewage run out.

When I removed the old black tank valve the rubber seal was broken into three pieces, rubber not flexible at all. That valve was not functioning.

[CRH]

Originally Posted by sheriff1

Maybe I'm missing something, I just bought an auxiliary valve that goes on where the hose attaches. Grey and black valves still function withe the auxiliary as the final stop.

That will work as bandaid for leaking waste gates. However, many of the problems people have come from the tank adapters that go between the valves and the tank. Both of mine were cracked.

[Wingeezer]

Originally Posted by A W Warn

1. I started out using Wiss hand shears (aviation type) but had a difficult time with my arthritic hands. So I purchased electric nibbler shears from Harbor Freight. The same as CRH mentioned above for ~$40. Not a great tool, but it got the job done.

2. Valterra did not have a direct replacement valve with the offset extension rods that are required to extend the handles to the exterior on my trailer. (at least I could not find one)

3. The flanges of the old waste tank adapters were cracked around the bolts. 18 year old plastic looked bad. It only cost a few $ for new adapters, so it made sense to replace them. On my trailer the tank has a coupler built into the tank, though it will not receive 3" pipe. The waste tank adapter slips into the tank coupler. The slip joint is sealed with waterproof caulk and clamped with a heavy duty hose camp.
The adapter connects to the Thetford valve using 4 SS bolts. There is a rubber ring washer on the valve that compresses as the bolts are tightened. On my trailer the sewer pipe fitting glues directly onto the valve outlet.
This is the tank adapter I used:
http://odmrv.com/catalog/index.php?m...oducts_id=1092

There is a rubber coupling that connects the elbow fitting to the combination wye fitting. I originally thought this was for ease of installation. During the installation I realize this rubber coupling separates the tanks from stresses. The tanks have a lot of flex, between empty and full levels which could crack the plastic parts. Stresses while traveling could break the plastic parts. I am mentioning this because I have seen one installation where the coupler was eliminated.

Many thanks indeed Alan, very helpful info.

[mschneid]

Auxiliary valve is like they said a bandaid. I’m needing to replace the valves as well and not looking forward to it. I’m using the auxiliary for now and will tackle this next summer.

[Jigs]

Getting ready to do this to my 98' Excella this weekend. Thanks for documenting. It makes it much easier.

I see you used cleaner/primer. I want to add to this useful thread by bringing to attention, ABS should never use primer. Cleaner yes. Primer and or Cleaner/Primer is never to be used.

source https://www.oatey.com/125878/Categor...ers-&-Cleaners

I only want to bring attention to this, as this thread is sure to help many. Thank you

[A W Warn]

Originally Posted by mschneid

Auxiliary valve is like they said a bandaid. I’m needing to replace the valves as well and not looking forward to it. I’m using the auxiliary for now and will tackle this next summer.

Originally Posted by Jigs

Getting ready to do this to my 98' Excella this weekend. Thanks for documenting. It makes it much easier.

I see you used cleaner/primer. I want to add to this useful thread by bringing to attention, ABS should never use primer. Cleaner yes. Primer and or Cleaner/Primer is never to be used.

source https://www.oatey.com/125878/Categor...ers-&-Cleaners

I only want to bring attention to this, as this thread is sure to help many. Thank you

How did it go? Any photo's to share?

Jigs, you are correct about the cleaner on ABS, not primer (clear, not purple).
This stuff works on any plastic sewer pipe > https://www.oatey.com/2371662/Produc...-Clear-Cleaner

[Julie-Bob]

Thanks for all information and photos. Our 2009 25’ Classic black water has started to leak. So it’s time to replace. Thanks

[A W Warn]

You are welcome!
Please share photos of your experience.

[Julie-Bob]

Will do. I’m going to purchase a power sheer to cut the pan

[Julie-Bob]

Well I replaced my black water tank drain valve today. As starters we have a 2009 25’FB Classic Limited. I read Rick March article in the November Blue Beret, in this article he stated that all Classic use the Thetford valve, not in my classic the Vallerra was installed, and all tanks were set in the tank pan with 1/2 foam insulation, not on my Classic (no foam between the pan and tank, also tank was 1/2 from pan, not on my Classic the black water valve in contacting the pan, to replace the valve I cut a hole 12” X 12” to change out the black water valve. Attachment 1