Gray Water Plumbing Question

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New member
Jul 6, 2006
Do all campers have gray water holding tanks?
If not, how do you collect the gray water?  Is there a "standard" fitting that can be used?
On campers WITH gray water holding tanks - if you want to collect the water externally to make it easier to dump, is there a bypass valve for the grey water or do you need to keep the grey water trap open and collect if from there.
Curious Canadian


Jan 13, 2005
Most RVs have grey water tanks, but some smaller ones may not. In the latter case, folks use a "Blueboy" rolling waste tank to collect the waste water.

For those that have a grey water tank, if you wish to continuously drain the grey water, the relevant flush valve needs to be open. You can either hook up a regular sewer hose, or you can buy a cap for the sewer connection that has a garden hose attachment.

Gary RV_Wizard

Site Team
Feb 2, 2005
West Palm Beach, FL
Some small ones, mostly the smaller pop-ups, do not have holding tanks for gray waste water. They usually have a standard hose fitting on the sink waste line an dpeople typically put a short hose into a bucket to catch the waste water (or if nobody is looking, they may just let it run on the ground).

Rvs with holding tanks do not usually have a bypass for the tank - at least I've never heard of one.  But there is a commonly available adapter for the end of the 3" drain line that allows a standard water hose to be connected.  That would allow you to drain water off into another container if you wanted. 

They also make portable waste containers, called "blue boys" because they are usually blue plastic) that accept a standard 3" RV waste drain hose. They have wheels and come in sizes from 10-40 gallons.

John From Detroit

Well-known member
Apr 12, 2005
Davison Michigan
Adding to what Roamer said about the "Blue Boy" waste water tanks.. The smallest ones (5-10 gallon) you are supposed to pull to the dump station by hand, As they get a little bigger (15 to about 40 if memory serves) you can get an optional adapter so you can tow them with your car, I have said adapter modified for use with a smaller tank

And the very largest ones come with a hitch adapter as standard.  These are very useful tanks.  I used one for gray water on my Pop Up and later on my Scamp (The pop up had a 1 1/2 inch IPT gray water outlet, the Scamp standard garden hose) the blue boy takes the garden hose (Washing  machine hose actually) no problem,  I had to build an adapter for the older popup, again, no problem, all standard pipe fittings
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