Winterizing Black Tank Flush

[MrJackSprat]

My wife saw an email from our local dealer not to forget to winterize the black tank flush line. We have never done this and don't see a reason to do so since line is not pressurized. Anyone have any insight if this is recommended or not?

[Robbbyr]

I have always blown mine out with air on my current and previous two units. Never had any issues.

I suppose it might be necessary to somehow winterize it in case there was any water trapped in the vacuum breaker/check valve. If the valve froze and broke, there could be a mess inside the unit (where my valve actually is located) the next Spring when I went to use the flush.

[Harvard]

I am mindful of the issue in our unit except any water left after using drains back and out because it is all downhill (from top of black tank to the point of water supply connection). Unless you know for sure there is no water in the pipes best be safe then sorry.

[troutslayer]

Thanks for reminding me

[Wertles]

I used compressed air to winterize mine. I was surprised at how much water was in the line still before it blew air.

[geezerbob]

I would like to hear more about winterizing the black tank flush. I didn't see anything in the owners manual about this on our 23rlsw.
I blew out all the lines then added antifreeze to the system, but not the black tank flush.
Did you blow it down then add rv antifreeze or ???
Critical or??
Bob

[JohnWedell]

I blow it out then add antifreeze with a hand pump. Antifreeze 50 cents, piece of mind priceless.

[Love To Travel 2]

I use compressed air, around 30 psi, to blow all the lines, including the outside shower and the black tank flush. I made an adapter using a male hose end, a short piece of garden hose and a fitting from my compressor. It gets screwed into the water intake and I let the air do all the work. Then I use RV antifreeze everywhere except for the black tank flush.

[geezerbob]

Why not antifreeze in the black tank flush?

[33 RLDS]

I never did anything to mine in 5 years with no issues. Maybe I have been lucky.

[Robbbyr]

Originally Posted by geezerbob

Why not antifreeze in the black tank flush?

You can if you have a hand pump to push it through. Just make sure you pump enough to fill the lines, vacuum breaker/check valve, and the flusher itself.

[RVhiker]

Originally Posted by 33 RLDS

I never did anything to mine in 5 years with no issues. Maybe I have been lucky.

Me too.

I think that due to the design of the black tank washer piping - with the vacuum breaker way above the tank sprayer and trailer side inlet - that any water in the piping has to either run into the tank, or out the inlet connection. Thus, no water stays in the black tank washer piping and no issue with cold weather.

[Iraqvet05]

Originally Posted by 33 RLDS

I never did anything to mine in 5 years with no issues. Maybe I have been lucky.

x2

[crumgater]

Originally Posted by RVhiker

Me too.

I think that due to the design of the black tank washer piping - with the vacuum breaker way above the tank sprayer and trailer side inlet - that any water in the piping has to either run into the tank, or out the inlet connection. Thus, no water stays in the black tank washer piping and no issue with cold weather.

After flushing, we ALWAYS get a heavy stream of water "leaking" out the inlet, so I'm 100% sure in our '15 Seneca TS, the flush lines gravity drain out the inlet.

We'll be sure to blow those lines with air, as well, just to be safe, though.

[Robbbyr]

Originally Posted by crumgater

After flushing, we ALWAYS get a heavy stream of water "leaking" out the inlet, so I'm 100% sure in our '15 Seneca TS, the flush lines gravity drain out the inlet.

We'll be sure to blow those lines with air, as well, just to be safe, though.

As a (demented!) Seneca owner who has "disassembled" a lot of my underbelly to add SeeLevel tank monitors and a hot water recirculation system, I got to see exactly how my unit's black tank flush was plumbed. From the wet bay inlet connection it ran forward to the wheelwell area where it elbowed up under the bathroom sink. That is where the vacuum breaker/check valve is located. From that valve it returns back down above the wheelwell where it then comes rearward into the wet bay/black tank compartment. Then it travels across the unit to connect to the black tank sprayer. In that line across the framerails it had a big "swale", enough to trap several cups of water before rising again to the sprayer itself. I did secure it up while I was there so it might better drain itself from now on.

I too always got water coming back out of my flush inlet when I disconnect, in my case I am pretty sure it was only draining the line up to the vacuum breaker valve. After the valve I am fairly certain I was trapping water. While PEX is somewhat freeze-tolerant, I am glad I was always blowing out that line with air as part of my winterization routine!