Break & Test - Black/Gray drain and holding tank

erond · Jul 3, 2008

I've managed, after many years of towing, to have an "oops". I took a corner too tight and a landscape rock took a bite out of the left side of my new North Trail 26RKS.

The black/gray combination drain was pulled (not broken) off cleanly. There doesn't appear to have been anything sealing it to the T/valve fitting.

I filled the black and gray tank and didn't see any evidence of leaking. I left the cap on and opened the valves and there is a leak where the drain pipe attaches to the T.

Is the drain tube designed to not use any sealant and I've seriously broken something, or should I just reinstall it with ABS cement or RTV? Note that the T fitting with the dump valves rotates smoothly around the black and gray tank drains.

I filled the black and gray tanks by hooking up to city water and leaving the sink on and holding the flush valve open on the toilet. It took "forever" and I never got the gray tank beyond 2/3 full on the gauge. To my surprise, however, the air vent for the plumbing was overflowing at the back of the trailer! I don't understand how the vent could be overflowing if the sink drain was still flowing freely.

Thanks for any input.

erond · Jul 4, 2008

I was able to take a closer look at the drain, and the joint was cemented, but pulled cleanly apart. I'm still thinking some RTV sealant would be an acceptable repair. I can cut the drain tube a little short to give a clean surface to cement, but don't see any way of cleaning the fitting still on the trailer.

I'm also still unable to fathom how the sinks/shower vent was able to overflow with water when the sink itself was still draining freely.

Ray LeTourneau · Jul 4, 2008

erond, the plastic plumbing fittings used in RV's use the same cement as PVC. RTV sealant doesn't wotk well on plastic. It may seal but not a very strong bond to hold it together. I'm not sure of the configuration on your trailer but it may be best to get a replacement valve if the broken one has pipe in it.
Do you have 2 grey water tanks? One for kitchen and one for bath water? This would be the reason for the rear vent to over flow. There may be a separate vent for your kitchen sink under the kitchen countertop.

Forrest Fetherolf · Jul 4, 2008

PVC glue and ABS glue are not the same type glue and are not interchangeable. PVC pipe is white, ABS pipe is black. PVC can be glued to ABS with a special glue for that purpose only. RTV glue will not bond ABS joints.
If the fitting will slip over the pipe, apply ABS glue to both pieces and hold in place for a few seconds until set, after glue dries apply a second and third coat around fitting and pipe to reinforce the joint.

Forrest

erond · Jul 4, 2008

Ray,

I'm going to see if I can clean up the join and use cement. One side of the break is naked pipe and the other is in a slip-joint like pocket with a ridge inside that mates with the pipe. I'm looking mostly for a quick-fix right now because we have a trip scheduled next week. A permanent fix would be cleaning or replacing the joint and re-cementing it.

I do have a second gray tank for the rear kitchen, but the vent I'm talking about is the one on top of the trailer the feeds the 1-1/2" PVC to get air into the drain system. It should be "impossible" for water to come out of a pipe that is 10' in the air when openings below it are flowing freely.

Thanks,
Rick

erond · Jul 4, 2008

Forrest,

Yes, the fitting is like a slip-joint, but the joint separation and and cement were on the butt-ends of the pipe and a ridge inside the slip.

I'm not sure how well ABS cement will help me since the surface of both pieces is already pitted from what looks like a pretty light original application of cement.

Rick

Ray LeTourneau · Jul 4, 2008

Forrest, I stand corrected. I assumed they were the same and I've used what I thought was PVC cement on the black pipe connector. It seems to be holding very strong. Our trailers connection wasn't square so when I used the 45 degree hose adapter to the rear it was always pitched up before going down. To the front it was OK because it was pitched slightly down. I cut off the connector and replaced it with the same type but put it on plumb so that when I was connected either front or rear I didn't get any liquids sitting in the connector.
Erond, could the vent on the roof be from the Black Tank? I would think it may be possible to fill the tank with the flush valve and I know water seeks it's own level but it would be easier to push water up a 1-1/2" pipe than back up the toilet/sewer pipe. It had to come from somewhere??? Check under your kitchen sink for a vent. It is a black pipe with a check valve vent on it. That should be your galley tank vent. I realize this sounds a little goofy but it's purely speculation at this point. I don't know the particular layout of your trailers plumbing vents.

erond · Jul 4, 2008

Ray,

I was connected to city water, not the black tank flush.

The rooftop vent the water was coming out of is directly connected (via Ys, Ts, etc) to the kitchen sink and presumably to the bathroom sink, shower, and commode.

I had my foot holding the commode valve open and the sink running in the bathroom. Water was flowing freely through the drains. I went outside a couple of times to check for leaks under the trailer and that's when I noticed the vent was dripping.

Ray LeTourneau · Jul 4, 2008

erond said:
Ray,

I was connected to city water, not the black tank flush.

The rooftop vent the water was coming out of is directly connected (via Ys, Ts, etc) to the kitchen sink and presumably to the bathroom sink, shower, and commode.

I had my foot holding the commode valve open and the sink running in the bathroom. Water was flowing freely through the drains. I went outside a couple of times to check for leaks under the trailer and that's when I noticed the vent was dripping.

I understand what you are saying and when I used the term flush valve I was referring to the foot flush on the toilet. In your original post, you indicated you had all the tank valves open and the cap on the outer dump pipe. With all the valves open any water filling the black tank will backflow through into the grey tanks through the dump valves you said were open. This would cause water to rise in a smaller diameter pipe, I can't answer as to why the sinks and showers would drain freely. Like I said earlier, purely speculation on my part.

Forrest Fetherolf · Jul 4, 2008

erond said:
Forrest,

Yes, the fitting is like a slip-joint, but the joint separation and and cement were on the butt-ends of the pipe and a ridge inside the slip.

I'm not sure how well ABS cement will help me since the surface of both pieces is already pitted from what looks like a pretty light original application of cement.

Rick

Rick,

ABS glue is pretty forgiving, if the fitting will slip over the pipe by 1/2" or more, glue it............the glue melts the ABS joints together. In home construction, I have applied glue to joints with pinhole leaks......it worked.

Forrest

erond · Jul 5, 2008

Ray LeTourneau said:
I understand what you are saying and when I used the term flush valve I was referring to the foot flush on the toilet. In your original post, you indicated you had all the tank valves open and the cap on the outer dump pipe. With all the valves open any water filling the black tank will backflow through into the grey tanks through the dump valves you said were open. This would cause water to rise in a smaller diameter pipe, I can't answer as to why the sinks and showers would drain freely. Like I said earlier, purely speculation on my part.

Ah. Sorry. It's hard to keep everything straight without being able to see what I was actually talking about.

There were two separate events. Drain valves and cap closed, filled both gray and black tanks. Sink/commode were still filling/draining freely when there was water coming out the vent. No leaking from the holding tanks. I was checking to make sure I hadn't broken the tank/drain fittings above the drain extension tube:

Code:

{Black}--Valve--Y--Valve--{Gray}
                |  (extension)
                V (cap)

With the valves closed, there was no leaking, but I got the "impossible" water out of the vent. When I left the cap on and opened the valves, it leaked between the "Y" and the extension tube (which is where I broke it).

erond · Jul 9, 2008

FWIW, I had some black RTV and it worked fine as a gasket (not cement). If it ends up leaking, I can either re-repair with ABS cement, or replace from the valves on down.

Haven't been able to duplicate the overflowing vent problem. I have no clue how/what happened there. I couldn't find any water behind the cabinets, on the floor, etc. when it happened.

Break & Test - Black/Gray drain and holding tank

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