Small Grey Tank drain pipe

Question

We have a 2014 Wind River TT ,with 2 drains for the black and the grey tank. The grey tank pipe is very small diameter compared to the black tank,for obvious reasons,but the grey tank takes for ever to drain. Is there a reason for making the grey tank drain smaller? I don't seem to recall that on other TT that we have owned. Thank you

mbopp · Answer

It seems to be industry practice to use 3" for the black tank and 1-1/2" for the gray.

tatest · Answer

I see this commonly on TTs and fivers, where the drain runs are long.Reason? Lower cost of materials?

old_guy · Answer

because water drains easier than solids.

hotbyte · Answer

Smaller gray tank piping on both our previous 5'er and current MH...

old-biscuit · Answer

it's not that the grey is so small it's that the black is large.

1 1/2" drain pipe is common for 'water'
3" is common for 'solids'

Pretty much the same set up in a house drain system.

Slow draining of your grey tank.......check for obstruction in grey tank vent line.

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Small Grey Tank drain pipe

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