Fuel 335 black tank issue

[mwatts0088]

Anyone one else have issues getting the black water tank to completely empty? No issues with valves or sewer pipe. The tank will drain to a point that appears to be empty. Then connecting hose & doing a sanitize rinse works with valve open and closed. Several cycles until water drains clear but no matter what I do there is always at least 5 gallons or more of waste water that will not empty. I’ve tried tilting the trailer to the drain side, nose high, nose low but still will not completely empty. Every time I get home I have to open the line & drive around my farm on uneven ground & do sudden stops & accelerations to try to slosh or force the remaining black water out of the bottom of the tank. I’ve had several rv’s but never had one that will not empty the tank. Is this a design flaw on the fuel 335?

Its just so so time consuming & frustrating. Always leaves an odor in the camper on the trip home because you can get all the waste water to empty. I have not removed the underlining to inspect the tank but it acts like the drain is not at the lowest part of the tank.

 

[danemayer]

I think you may find the center of the tank is sagging, allowing some water to pool there. My gray #1 has a significant sag from being completely filled over and over for years. I can't see the bottom of the black tank, but it wouldn't surprise me to find sagging there as well. I don't think it's all that unusual.

Sounds like maybe the real question is why do you have an odor inside when there's a few gallons of water left in the black tank.

You might want to check for other sources of odor. Studor valves in the kitchen or bathroom are often the source. Studor Air Admittance Valves allow inside air to go down the drain (acting like a roof vent). If they fail, air from the tank will enter the interior rooms. The gray tanks can stink pretty badly.

 

[mwatts0088]

I think you may find the center of the tank is sagging, allowing some water to pool there. My gray #1 has a significant sag from being completely filled over and over for years. I can't see the bottom of the black tank, but it wouldn't surprise me to find sagging there as well. I don't think it's all that unusual.

Sounds like maybe the real question is why do you have an odor inside when there's a few gallons of water left in the black tank.

You might want to check for other sources of odor. Studor valves in the kitchen or bathroom are often the source. Studor Air Admittance Valves allow inside air to go down the drain (acting like a roof vent). If they fail, air from the tank will enter the interior rooms. The gray tanks can stink pretty badly.

Thanks for the info. Trailers less than a year old so a sagging tank would be frustrating but your suggestions makes sense. When the weather warms up I’ll try to pull the undercarriage back & look for that issue. Perhaps I might be able to install an extra brace if needed.

 

[avvidclif]

To add. After draining the black tank and rinsing like you describe I put in several gallons of water and add the chemical. No smell and ready for next trip.