Frozen black water rinse line

Tumblebug

Well-known member
I had used the MPG over the Holidays as a spare bed room, nice and cozy, warm, sat tv. Used bottled water. It's a nice day in the mid 60's, so I thought it's a good day to give the black water tank a good rinse before putting the MPG in the barn. I did not blow the black water rinse line out or pump rv antifreeze through it when doing the fresh water system in October. It froze and ruptured. A word of warning "do not" neglect the black water tank rinse line when winterizing.

Now I have a repair job to do this winter. :eek:
 

marc515

Well-known member
Wow, I never gave a thought about putting antifreeze in the Black Water Flush Line, as I thought it would have been a straight drop into the tank. However, I just looked at the line today, and it is not a straight run, and it reduces to the small type lines, so antifreeze looks to be necessary.

Anyone else experience this?

I'm going to pump some antifreeze thru my black water flush line tomorrow.

Thanks for the heads up
 
Last edited:

steveo

Member
thankyou
i just blow it out today and i think is ok,it got up to 48 so i put the heat on and then blow it out,nothen came out of the drain so i think its good.
 

Tumblebug

Well-known member
There is a wiki on the black tank flush system, as far as I can tell so far, the first simple diagram is close to the system in the MPG. MY current guess is that the vacuum breaker is what frozen and cracked. The inspection port is in the pantry, back side of bath room sink. Will update when I pull the inspection cover off. So far this is just speculation on my part. Any help would be appreciated. Link to the Wiki
//heartlandowners.org/mediawiki/index.php?title=Black_Tank_Flusher#Block_Diagram
 

TedS

Well-known member
I would guess there is a sag or a low point in the hose between the connection port and the vacuum break valve and the water did not completely drain back out the connection like it was supposed to.
 

PeternLiane

Well-known member
Never thought about blowing it out. We are more than an hour away from the storage. Will have to wait till we get up there. We only used the NT once before blowing the other lines. Thank you for the heads up. I will remember it from now on.
 

Tumblebug

Well-known member
I may have reached the wrong conclusion about the black water line freezing. It looks like it is a faulty vacuum breaker/check valve. The valve apparently stuck and allow the water to come out of the top of the check valve. MY valve was a B&B model 571 110P , 125 psi, 1/2 inch threads. The Wiki has a very good diagram of the system. Thanks Mr. Jim.
I still believe it would be a good idea to blow out the black water flush line. When I took out the valve there was water in and around the valve.

On the MPG you can access the valve and the bath sink drain by the inspection panel in the pantry at least in my MPG 183.
 

Tumblebug

Well-known member
That's my best guess, I examined the valve and the float mechanism was stuck open due to the little ball wedged against the valve wall keeping the valve from operating.
 

Bob&Patty

Founders of SoCal Chapter
Tumble, you might see if you can find a brass valve for a replacement. I do believe they make them.
 

wal_mart

Active Member
My new unit, the black water rinse line goes downward almost a foot before it goes up to the check valve. Very good area for water to pool and freeze.
 

Boca_Shuffles

Well-known member
For people with BH 3055's, the rinse line goes up directly from the UDC to the valve behind the shower. The line then goes down to the black water tank. Gravity will keep your line clear.

I know this because I went and checked my unit that was in storage, just to make sure.

Thanks for the good tip/reminder for other units.
 
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