Black tank

[Bigbur]

I was pouring water with Borax down the toilet as the black tank was being pumped out. Somehow the water got up onto the roof and came over the side and almost hit the kid pumping it out. Can anyone explain how that happened? Any permanent problems as a result of the spilling out onto the roof now that the black tank is empty?
Thanks

[16ACE27]

The black tank (and gray tank) are both vented to the roof. If water was being pumped into the black tank instead of out of the black tank it should come up your open toilet and even the bathroom sink long before it came out of the roof vent. And, of course, the honey wagon should have been sucking on the black tank, not pumping to it.

Rinse the overflow, Borax shouldn't hurt anything but it may streak the sides if left on there.

[Bigbur]

The black tank was being pumped out not into. I was pouring down the toilet the water. I never knew it vented to the roof. Hopefully it should only be the water Borax mix and not the fecal sludge.

[Bill Johnson]

Originally Posted by Bigbur

I was pouring water with Borax down the toilet as the black tank was being pumped out. Somehow the water got up onto the roof and came over the side and almost hit the kid pumping it out. Can anyone explain how that happened? Any permanent problems as a result of the spilling out onto the roof now that the black tank is empty?
Thanks

Here is an interesting website talking about all the things people put down rv toilets. https://uniquecampingmarine.com/blog...myths-debunked

[Bill Johnson]

Originally Posted by Bigbur

The black tank was being pumped out not into. I was pouring down the toilet the water. I never knew it vented to the roof. Hopefully it should only be the water Borax mix and not the fecal sludge.

Read the story I posted, it turns out most of the things people use don't work or stop the rv stuff from working

[Judge]

Originally Posted by Bigbur

The black tank was being pumped out not into. I was pouring down the toilet the water. I never knew it vented to the roof. Hopefully it should only be the water Borax mix and not the fecal sludge.

Depending on how strong their pump was, it may have created negative pressure vacuum in the tank... even though it is vented. When you opened the toilet you allowed atmospheric pressure to rush into the tank and it then pushed anything it could find out the vent.

We do not treat the tanks until after dumping and flushing. Otherwise whatever you put in is going down the drain... so to speak.

[Bob Denman]

https://www.youtube.com/watch?v=-C0bpTLEmZw

[Bill Johnson]

Is this what it looked like

[Bob Denman]

https://www.thorforums.com/forums/at...1&d=1660913439

[The Gritz Carlton]

Originally Posted by Judge

Depending on how strong their pump was, it may have created negative pressure vacuum in the tank... even though it is vented. When you opened the toilet you allowed atmospheric pressure to rush into the tank and it then pushed anything it could find out the vent.

We do not treat the tanks until after dumping and flushing. Otherwise whatever you put in is going down the drain... so to speak.

That's exactly what happened. Turd pumper trucks are designed to pump septic tanks upward as much as 8 feet...its a really strong pump. They operate way too strong to be pumping on a closed system like an RV tank. We use this service at the race track over the 10 day stay. I ALWAYS tun the water off and have someone hold the flush valve open so the tank walls don't get sucked in.

[Judge]

Originally Posted by The Gritz Carlton

That's exactly what happened. Turd pumper trucks are designed to pump septic tanks upward as much as 8 feet...its a really strong pump. They operate way too strong to be pumping on a closed system like an RV tank. We use this service at the race track over the 10 day stay. I ALWAYS tun the water off and have someone hold the flush valve open so the tank walls don't get sucked in.

Great advice on holding open then flush valve!

I have read posts about guys having the tanks sucked in and even cracking as a result.

The vent on the roof is just not big enough to keep up with that pump.

[Travelin' Texans]

Originally Posted by Judge

Great advice on holding open then flush valve!

I have read posts about guys having the tanks sucked in and even cracking as a result.

The vent on the roof is just not big enough to keep up with that pump.

That's it!
A 3" hose with serious vacuum & a 1 1/4 - 1 1/2" vent trying to keep up. In this case s##t will go uphill!
FYI! If you're dumping your tank treatment into the toilet while the truck is pumping you just as well dump it directly into the truck. Wait til the truck is finished then put the treatment down the toilet.

[Geterdun]

Originally Posted by Bigbur

I was pouring water with Borax down the toilet as the black tank was being pumped out. Somehow the water got up onto the roof and came over the side and almost hit the kid pumping it out. Can anyone explain how that happened? Any permanent problems as a result of the spilling out onto the roof now that the black tank is empty?
Thanks

Ask the kid doing the pumping. Did he backflush the hose with fresh water?

Because all these answers claiming that fluid will only go out the highest point in the system against gravity and against the flow of air from high pressure (atmospheric pressure) in 3 locations (vent, toilet, sink) to the vacuum source do not understand physics, fluid dynamics, and Pascal's law.

[Jimbo56]

But guys, he had the flush valve open pouring liquid in.

[16ACE27]

Originally Posted by Geterdun

Ask the kid doing the pumping. Did he backflush the hose with fresh water?

Because all these answers claiming that fluid will only go out the highest point in the system against gravity and against the flow of air from high pressure (atmospheric pressure) in 3 locations (vent, toilet, sink) to the vacuum source do not understand physics, fluid dynamics, and Pascal's law.

Wut he said....

[Judge]

Originally Posted by Jimbo56

But guys, he had the flush valve open pouring liquid in.

The question is when did he open the flush valve. As soon as they started pumping or close to the end?

[Judge]

Originally Posted by Geterdun

Ask the kid doing the pumping. Did he backflush the hose with fresh water?

Because all these answers claiming that fluid will only go out the highest point in the system against gravity and against the flow of air from high pressure (atmospheric pressure) in 3 locations (vent, toilet, sink) to the vacuum source do not understand physics, fluid dynamics, and Pascal's law.

Since you don't think water could end up on the roof via a large change in pressure from negative pressure to positive pressure...... If the kid was back-flushing the hose with fresh water, wouldn't he then get a blast in the face at the toilet since that is the lowest point?

[Geterdun]

Originally Posted by Judge

Since you don't think water could end up on the roof via a large change in pressure from negative pressure to positive pressure...... If the kid was back-flushing the hose with fresh water, wouldn't he then get a blast in the face at the toilet since that is the lowest point?

Correctamundo!

[The Gritz Carlton]

Originally Posted by Jimbo56

But guys, he had the flush valve open pouring liquid in.

The simple act of pouring water in while the pumper truck was going will cause the same problem I outline a few posts ago. The water he's pouring down the toilet will actually "close" off the airflow necessary to prevent back pressure. Those pumper trucks will empty a 1,000 gallon septic tank in 5 minutes. That's a lot of "flow" for a tank that doesn't have a free-flow of air from the intake. Kinda like a Food-Saver on steroids.

[Shanks12]

Maybe silly question.. But are you sure it was the water/borax mix that that ran down the side?

Could this just be a simple shift in weight due to the tank being emptied that water from the AC's ran off the side?