Grey Water and Sullage Drainage
One of the banes of every caravan’er’s existence at one point or another is the slow or lack of adequate drainage from the vans sink and shower etc via the vans grey water sullage/waste outlet and connected pipe. At the risk of being Capt Obvious a smooth, unrestricted and a continuously descending flow path is paramount. Jaycos for example seem to excel at getting each of these, if not all of these wrong and have a history of Coco Pops and pasta noodles put down the sink somehow popping up in the shower.
There are a few simple and quick fixes to help with flow, along with some more elaborate solutions to deal with waste backing up. Way to often you’ll come across caravan parks where the path from the site to the grey water sullage point is all uphill.
Generally the highest point of a caravans sullage path is the sink waste which is also the most frequently used. One common issue with 25mm sinks wastes is the elbow if there is one fitting directly under the sink. The inner screw-in top section, which seals into the base of the sink bowl can penetrate too far into to the corresponding elbow section under the sink and effectively acts like a gate valve by reducing the elbow opening by anything up to 3/4 its diameter. With 25mm sinks wastes look down the plug hole, or poke a finger down and feel for the fully clear 25mm right angle into the elbow bend. If its not fully clear the top section can be screwed from the lower section and the length of the threaded top section be reduced so it doesn’t screw down past the elbow bend.
Another common issue is the dreaded sullage pipe hump that forms when the caravan park waste requires the sullage hose to be placed vertically into the receptacle forcing the sullage hose to hump into the air causing a gravity challenge to running waste to force its way over. The hump can be completely eliminated with a 25mm garden irrigation poly elbow attached to the end of the sullage hose helping the sullage pipe to lay flat over the ground; even better is to add a short length of 25mm garden irrigation poly pipe to the elbow and put down the drain. Just sand, cut or grind the barb off the exposed end of the elbow so it will easily slide into the end of the sullage pipe..
Arguably the easiest and cheapest way to give the vans waste the best leg up is with the use of a sullage sump. A plastic tub of 10 to 20lrs is ample, and that tub sits unconnected but directly below the vans waste outlet, and the sullage hose is then connected to the tub. Waste leaves the vans system, dropping into the tub to drain away at its leisure. The tub provides the additional task of storage of tap and waste fittings when not in use and eliminates any backup of grey water waste into the van
We have taken that sump system one step further. Our sump also has internally fitted a submersible auto 12v boat bilge pump. The tub itself has 2 x 1 inch outlets, one directly connected to the pump and the other just for regular free flow draining. We attached the sullage hose to the most appropriate outlet dependent on the site requirements, pump for uphill and free draining for flat ground. The pump is very handy for those strange caravan parks that install the waste inlets higher than the site which renders gravity drainage useless. Our auto submersible 12v boat bilge pump is a Seaflo brand and cost around $25. The Seaflo is powerful enough to pump water over 12ft vertically a maximum of 50ltrs per minute. Its a cheap and very effective pump which activates automatically when the grey water enters the tub; no or minimal user input which is a mandatory prerequisite for all our modifications and additions.
Testing the auto submersible 12v boat bilge pump before finding the perfect tub, installing pump and putting the completed system into service
Our final design is a 10ltr rectangle plastic box with our Seaflo 12v auto pump mounted inside. The gravity flow is on the opposite side of the tub, and the tub serves to store our water and waste fitting when we’re not using it.
