New trailer and slow draining black tank

**Mr. Goodwrench** · 09-20-2018, 11:51 AM

As the title says, before even using the plumbing in our new 29rs, I was hooked up at a campground on our shakedown trip and added fresh water to the black tank mainly through the flusher. I thought I had added plenty to flush the brand new tank but when I pulled the drain handle, all I got was a very small stream coming out of the discharge. I have a clear elbow on the hose so I can see the flow. On our old trailer, I would get a real gush of water for some time depending on how full the tank was. I kept working the handle and the valve is closing and the pull seems long enough to indicate the valve is opening all of the way.

After adding more water directly down the toilet and through the flusher I tried again. Still not seeing the rush I would expect. I have heard horror stories of owners finding out that the cut out piece of tank from the installer cutting the hole for the plumbing has fallen into the tank and not removed. Of course this piece finds it way to the discharge outlet and blocks the opening. Because we had to continue our stay on this trip, I added my chemicals to the black tank and started using the facilities. When it was time to leave, I did my best to flush and drain the tank but I am sure there is still stuff remaining.

We have another trip reserved in a week so I have made up a homemade version of a "flush king" using a cap with a hose fitting in it along with an add on waste valve. We will have full hookups so the first thing I will do after setting up is start back flushing my tank at the outlet. I know it won't remove the obstruction especially if it is the cut out piece but hopefully it will allow me to get more of the contents out of the black tank so we can use the bathroom and not over fill the tank. Also when we leave, I want to get the tank as empty as possible since the next trip will be back to the dealer to let them deal with the problem.

Does anybody have any suggestions of more things I can try besides what I will attempt next week? Thanks in advance.

**TucsonJim** · 09-20-2018, 11:58 AM

Just brainstorming here. For $36, you could purchase the endoscope linked below and do a visual examination of the pipe and tank to make sure there are no blockages. At 11-1/2' long, it should be able to access the areas you're concerned with. Of course, I'd sure drain that tank to the best of my ability before proceeding - LOL.

https://www.amazon.com/dp/B01MYTHWK4...537466144&sr=1

Jim

**SouthTX** · 09-20-2018, 12:00 PM

Perhaps a snake from the discharge end? Might knock something loose.

**Second Chance** · 09-20-2018, 01:35 PM

On a brand new RV, I'm afraid construction debris might be the culprit. The scope that Jim provided the link to is a good option. It's a warranty issues, though. How far are you from your dealer?

Rob

**WhittleBurner** · 09-20-2018, 02:48 PM

Rob has a good suggestion. We had the same issue with our kitchen Gray tank when we first got it aand it seemed to happen off and on for about aa year. We picked up the clear extension with the ability to back flush (like the Flush King) and remove the obstruction when it did happen. It hasn't happened again in a few years (knock on wood)

**RVRunners** · 09-20-2018, 05:47 PM

There is a good chance this could be an issue with the vent for the tank. I recommend going on the roof and checking/removing the vent cap to see if the vent pipe down too far in the tank. You will be able to move the pipe up and down, however, it is critical not to pull it up too much to avoid pulling it from the top of the tank. Just pull it up slightly and see if the discharge performance changes. You may need to drop the coroplast in the tank area to check the bottom end at the tank. It is possible that the vent pipe could be at or close to the bottom of the tank which will not permit air admittance and therefore proper draining of the tank. Think of a drinking straw - you can place your thumb over the top of a straw, pull the straw out and walk around the room with a straw full of soda without dumping it on the floor - remove your thumb and you have a mess. Plumbing ventilation in your RV and home works the same way. Good luck!

**jasonl78** · 09-20-2018, 06:31 PM

If you have a helper, have them go inside the unit and step on the pedal of the toilet and watch your clear elbow to see if you notice a difference in flow. I also suspect venting may be the issue.

**Mr. Goodwrench** · 09-20-2018, 08:28 PM

Thank you all for the suggestions. I will be set up in a campground next Thursday and will come prepared to do more investigation. Will let everyone know what I find out.

**Buckskin** · 09-21-2018, 05:06 AM

I think above advice is great. Can only be 1 or 2 issues; drain blockage or vent blockage. Follow advice from above post should solve your problem.
fyi my grey tank vent for kitchen tank is not on top of camper but on back wall. Black water vent should be on top of camper as you need plenty of air flow from vent for tank to drain correctly.

**clubsmity** · 12-13-2018, 08:09 AM

I had a similar experience doing the same procedure when I first picked up my unit. Both the gray shower tank and black tank took minutes of running water through the toilet and shower before starting to trickle out the discharge outlet. They both hold about 5 gal of heal due to the poor design in the soil pipe (discharge manifold) it actually goes uphill apprx 2" when leaving the tank outlet's. This has caused poor drainage. I would have to pull the black gate valve and then open and close the kitchen gate valve several time to help push along the LOG jam from the black tank. Then I would have to unhook the truck and raise the front of the trailer 6-8" to get the tanks to drain. I took it to my dealer to fix it and they said it works fine!!!? Then last month when we left the north in freezing temps my gray and black gate valves were frozen in the open position due to the heal left in the tanks. F my head.
When I pulled the belly skin down to see what GD did to cause this I discovered the problem. They ran the discharge pipe through the rear bulkhead frame channel which is approx 2.5 inchs higher than the outlet and gate valve of black and gray. So everything has to run uphill before leaving the trl. So unless the dump station is on hill I have to unhook and jack the front of the trailer up . Brilliant!!
So I decide to cut out the bottom section of the cross member frame channel which allowed the discharge pipe and entire manifold to lower to a relaxed position, and now allows a proper fall and drainage. Now have to round up some metal to weld up and reinforce the C channel bulkhead. Great having to fix stuff on brand new trailers!