Aroma

[FF]

"The outlet in a holding tank is at the bottom. You couldn't pump it out from the top, you would be sucking air."

Depends on how deep the suction pipe is.

 

[HeadMistress]

The outlet in a holding tank is at the bottom. You couldn't pump it out from the top, you would be sucking air.

Discharge fittings in the top of a tank, with a pickup tube inside the tank that goes to the bottom, are actually quite common because they eliminate standing sewage in the line from a fitting at the bottom of a tank. It requires at least 5" clearance above the tank, though, so it's not always possible.

However, what FF referred to, and what RV tanks have, is a discharge outlet IN the bottom of a tank. RV tanks aren't pumped out, they're dumped into inground storage tanks at "dump stations" in RV parks. Owners can install a system that washes down the inside of the tank walls...and in so doing, that also washes out the sludge in the bottom.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

 

[FF]

" RV tanks aren't pumped out, they're dumped into inground storage tanks at "dump stations" in RV parks."

Yes that is what most folks do.

Others attach a macerator pump , have a 1 inch hose and can empty their tanks at home or visiting friends.

The delight of the RV setup is if a good shut off valve is chosen the either a simple hose for gravity discharge or a macerator pump can be installed with zero mess ,and almost no effort.

The RV folks frequently will chose a 120V pump (run from their inverter) which seems to have a far longer life than the 12v DC stuff..

The bottom , wet discharge is far easier to keep operating than a lift setup where dried gunk and paper can easily stop the suction .

While there are $10.valves at the RV store , sending off for good ones is worth the effort.

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[rwidman]

Discharge fittings in the top of a tank, with a pickup tube inside the tank that goes to the bottom, are actually quite common because they eliminate standing sewage in the line from a fitting at the bottom of a tank. It requires at.........

That is still at the bottom of the tank. The difference is, the tube is inside the tank so you can't see it, you have to imagine it.

Mine is on the outside on the side but at the bottom. I understand the point about standing sewage in the hose. I've thought of installing a piece of PVC tubing on the outside to the top level of the tank and connecting the hose to that but there are issues with that and I haven't really had a problem so it's just a thought for "someday".