Brand new RV: Gray water tank will not flush

[mcraig88]

Hello,


Our Alpine 3700FL has 2 gray water tank handles, and 2 black. One of the gray tanks will empty no problem, but the second one will consistently not drain. We've only been living in it for a week, but it has been very cold out (under 25F) the tank heaters are on.



The only way we've been able to get it to flush is to pour about 3 gallons of nearly boiling water down the bathroom drains, and then open all 4 handles.


I beginning to wonder if a heater isn't working properly, or maybe the handles are crossed, and a black handle opens the gray tank or some nonesense.





Very frustruating when you want to take a shower and water is backing up.



Any ideas?


Thank you!

[chuckster57]

Welcome to the forum

Sorry your having issues, easiest way to check handles/valves is to fill one at a time until at least the 1/3 light is on, then pull the handles one at a time to see which one empties the tank.

It’s a running issue with mis labeled tank handles, and in addition you may have a non operating heating pad.

[firestation12]

My 2019 3700FL has the pull handles arranged as follows: Black 1,Gray 1, Black 2, Gray 2.
Black 1 (closest to access door) dumps the forward black tank of the 1/2 bath by the kitchen. Gray 1 (2nd valve) dumps the galley sink and sink in the 1/2 bath. Black 2 (#3 valve) opens the rear black tank (the master toilet). The 4th valve (furthest from the access door) dumps the shower and lavatory sinks. If temps are low enough, freezing can occur in the plumbing under the shower drain and in the HepvO valve or p-trap causing water to back up. The HepvO valve also can get stuck shut from long periods of non use. I believe all tanks are in the 40 gallon range. Other areas of plumbing problems are anti siphon valves under the rear sink (next to the toilet) that may be installed backwards. Most of the plumbing under the rear bathroom has poor heating to protect the drains and pex pipes in cold weather. Not sure how savy you are about what tanks to never leave closed when in use (the black ones) or which can be left open when connected to a septic drain (The gray ones).

[travelin texans]

Originally Posted by firestation12

Not sure how savy you are about what tanks to never leave closed when in use (the black ones) or which can be left open when connected to a septic drain (The gray ones).

I think you meant NEVER leave the black valve "open" when connected to sewer, open valve & dump as needed. You can leave the the grey open, but close it a day or 2 prior to dumping the black to rinse the black leftovers out of your hose.

[adm1949]

I had the same problem. Turned out the plug that was cut out of the tank was left in the tank. The cutout ended up stopping it up. After flushing it out, the tank now drains fine.

[DonP]

Just an FYI and not a comment on the specific question. I changed the handles on my tank drain polls, the black tank has a black handle, and the gray tanks have the gray/silver handles. In case the decals ever come off at least I'll know which are which.

[firestation12]

[QUOTE:=travelin texans;488511]I think you meant NEVER leave the black valve "open" when connected to sewer, open valve & dump as needed. You can leave the the grey open, but close it a day or 2 prior to dumping the black to rinse the black leftovers out of your hose.[/QUOTE]

What was I thinking! Actually I typed out a reply and got interrupted and when I came back, I lost everything. It was tempting to just bag it, but after regaining my composure, I repented and redid the reply. As the saying goes, haste makes waste. Anyway, it’s nice to know someone critically proof reads these threads! Thanks TravTex!

[RickV]

Originally Posted by DonP

Just an FYI and not a comment on the specific question. I changed the handles on my tank drain polls, the black tank has a black handle, and the gray tanks have the gray/silver handles. In case the decals ever come off at least I'll know which are which.

Grey Duct Tape works too.