Getting gradient on the waste pipes

[RogerL]

Anyone who's done anything with domestic plumbing or building will know that a gradient of at least 1:100 is necessary to drain away waste water, etc or surface water - but it's a concept too difficult for caravan designers, at least those employed in the UK.

I've just spent a rewarding couple of hours on my back under the caravan fitting a 25mm and 50mm small wooden block between each of three waste pipes and the caravan floor so that they have a gradient slope on them instead of being screwed directly to the underside of the caravan floor - which now means that if I pitch the caravan level, the water should drain out of the kitchen sink, washroom basin and shower in seconds rather than minutes!

For those who remember Bernard Hill's character Yosser Hughes in the '70/80s "Boys From The Black Stuff" - a message to Bailey, Coachman, Elddis, Lunar & Swift - "Gizza job, I can do that!"

 

[Raywood]

I think we all know what you mean to get the ater to drain properly we would have to have the caravan leaning heavily to one side. It does seem to me that putting a slope on it would leave it too low to go in the waste water container and too near the ground as it has to cross from one side of the caravan to the other on ours at least or it would be in the awning.

 

[RogerL]

On my Lunar, the kitchen sink and shower wastes both come out underneath on the awning side and go across the caravan to waste outlets under the side skirt - measuring them, the top of each outlet is 100mm below the underside of the floor - so each of the pipe runs is dropped by my modification just 50mm at the end near the outlet, so there's a downward slope throughout their run - the waste outlets haven't been moved, so are no nearer the ground.

 

[Surfer]

I am not sure whether it si the solution or not? The difference between a caravan drain and a domestic drain is that a domestic drain normally has the U bend in it to faciltate draining. This for obvious reasons cannot happen in a caravan. In a caravan you have the water going down, but it has to get past all the air in the drain pipe hence slow draining. We have found that by twirling your finger in the water in a clockwise motion by the basin drain plug area facilitates the water emptying a lot faster.

 

[RogerL]

The reason for the air lock is all the water lying in the horizontal pipe because there's no slope !
Where the flexible hose comes through the floor it then curves back UP to meet the transverse pipe attached to the underside - this make a rudimentary U-bend and should shop draughts blowing in through the sink and shower drains.

 

[liam99]

My Abbey Spectrum has always had a very slow draining kitchen sink though both the shower and bathroom drained well. I have never before been able to get good access to the sink drain pipe under the van because of the twin axles and motormovers but recently jacked the van right up onto axle stands and removed the wheels in order to fit shock absorbers.

Whilst under the van I could see the "u-bend" in the plastic flexible pipe where the sink drain comes through the floor, as described in the previous post. I obtained a 28mm, 90 deg elbow and cut the pipe level with the underside of the floor. I removed the 300 mm of excess pipe and and fitted the new elbow giving a level pipe run under the van to the outlet. The water flow from the sink has dramatically improved, so a worthwhile modification I think.

 

[bertieboy1]

Surfer,
Have to disagree with you regarding the function of a U bend,it's there to -
1. Trap solids and prevent blockages further down the waste pipe
2.Stop smells coming up from the drain
3.Creates a barrier preventing germs coming up from the drain
It does nothing to assist draining.