Black Holding Tank slow to drain...
Our Black Holding Tank is slow to drain. Can this be caused by a bad Air Admittance Valve or a clogged vent cap or both? The tank dumps fine at first, but it eventually backs up and then very slowly...
Forum Discussion
Sewage systems generally are designed to be gravity flow (partially full pipes, alowing liquids to flow down while allowing gases to flow up using the same pipe), so if your line is full (potentially under pressure), that could be an un-fun day for you if the hose or connection ever leaks.
Sounds to me like the issue is with your sewage line, and nothing to do with your RV, since the flow is backing up in the hose (and presumably in the sewage pipe). Most likely there's a partial blockage somewhere in the sewer pipe, and when there's enough buildup of non-liquid materials at this choke point, it blocks it nearly completely (kind of like an ice dam effect). I suppose that if the line feeds to a septic drain field, its also possible that that system is just full and/or clogged, and can't keep up with demand. Or, its also possible that the system was designed poorly and there's no way for the sewer gas to escape, which could block new fluids from flowing down the pipe very quickly--you could tell if you see big bubbles working their way up the pipe against the flow.
In any case, I don't think that I'd try to keep diagnosing the problem using the actual black tank flow, so you don't have to deal with any leaks of that full pipe. I'm not really sure what I would do instead, though. Perhaps grind up some leaves and mix them in some water to simulate the solids? sounds like an issue the campground owners are going to have to take care of.
Sounds to me like the issue is with your sewage line, and nothing to do with your RV, since the flow is backing up in the hose (and presumably in the sewage pipe). Most likely there's a partial blockage somewhere in the sewer pipe, and when there's enough buildup of non-liquid materials at this choke point, it blocks it nearly completely (kind of like an ice dam effect). I suppose that if the line feeds to a septic drain field, its also possible that that system is just full and/or clogged, and can't keep up with demand. Or, its also possible that the system was designed poorly and there's no way for the sewer gas to escape, which could block new fluids from flowing down the pipe very quickly--you could tell if you see big bubbles working their way up the pipe against the flow.
In any case, I don't think that I'd try to keep diagnosing the problem using the actual black tank flow, so you don't have to deal with any leaks of that full pipe. I'm not really sure what I would do instead, though. Perhaps grind up some leaves and mix them in some water to simulate the solids? sounds like an issue the campground owners are going to have to take care of.
