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Mod #85: Grey Water Potty Flush

Posted By ModMyRV On July 22, 2009 @ 8:17 am In interior, plumbing | 32 Comments

This modification was designed and completed by Professor Randy T. Agee, D.Ed., April 2009, on a Cedar Creek 34SATS fifth wheel trailer. This article carries a copyright. Permission must be obtained from the author before duplication or reposting. Contact professor95@comcast.net

A fellow campin’ buddy and his wife had joined Nancy and I around the glowing embers of a campfire. We were toasting some marshmallows as I detailed the specifics of the modification described below. When I was finished with my description, I commented that in reality the modification was totally overkill as the same thing could easily be accomplished with a 2 gallon bucket from the Dollar Store.

David’s reply to my statement was novel, “You do it that way because you can”.

Mod Difficulty:

He was right. Many of the modifications I make to our RVs are done simply because I can. And why not? I enjoy dreaming up, designing and implementing these modifications. Of course, I am always careful not to do anything that will compromise safety or the structural integrity of the RV.

One of our favorite camping spots is at Big Meadows on the Skyline Drive in Virginia. The mountains are absolutely magnificent; the deer so tame they walk right up to your campsite and an occasional black bear may ramble down a nearby path. We generally make the trip up to the mountain at least twice a year.

Like many federal campgrounds, Big Meadows does not offer any hookups at the RV site. The campground’s dump station and potable water supply for RVs is almost a mile away. Thus, you must contain and pump your own water and deal with your waste by using the appropriate RV holding tanks.

Our fifth wheel camper has a 62 gallon fresh water tank while the bath, galley and toilet holding tanks are 40 gallons each, for a total of 120 gallons of waste water storage.

Depending on the length of our stay, we often have the need to refill the fresh water tank and remove waste water from the bath tank. The galley and toilet holding tanks are more than adequate in capacity for storing waste water for at least a week. Conservation of both our fresh water and bath tank waste water space is important if we wish to avoid time consuming refills and dumps using portable containers. Of course one way to accomplish this is simply not to shower. But, in our camper that is not going to happen. The wife likes clean bodies on our sheets and I do not like sleeping on the couch.

I got to thinking about this before we made our spring trek to the mountains and came up with an idea that evolved into a RV plumbing modification that I believed would save both fresh water and grey bath holding tank space.

What bothered me was how we used fresh water to flush the toilet. In my way of thinking this was wasteful. Why do we need fresh water when we have a tank full of slightly used bath water? If I could devise a simple method of routing bath tank grey water to the toilet I would not only save fresh water but I would reroute some of the bath tank water to the black tank, which really has excess capacity when dry camping.

The plan involved installing a cut-off valve so that the fresh water supply could be completely isolated from the potty’s water flush line. Water from the bath tank would then be pumped to the potty for flushing. A switch next to the potty would allow us to turn the pump off at night or when we reverted back to a fresh water flush system. This switch could easily be located next to the pump rather than on the wall. I just liked having the switch accessible.

I had an unused Shurflo 12 Volt DC diaphragm pump that I had swapped out for a more efficient microprocessor controlled variable flow pump a few months earlier. I mounted this pump on the utility wall in the basement of the camper (photo #1) and ran wiring for an on/off switch up through the floor of the potty area so it resides next to the potty (photo #2). Similar pumps are available from a number of suppliers. Northern Tool is one source that has pumps in the $50 range. You do not need a high flow pump. One of the smaller 40 psi pumps that provide 1 gallon per minute should work fine.

The next task was to cut into the water line to the potty and insert a cut off valve so that it would be totally isolated from the fresh water system when turned to the off position. On the potty side of the cut-off valve I added a “T” into the line that is connected to the output of the Shurflo pump with a brass 1/2″ NPT pipe fitting to 3/4” garden hose fitting (photo #3). This fitting was found at Lowe’s and includes its own cut off valve so that there is no backflow when I return to using the fresh water system. Since the water lines are PEX, you will need special fittings or the tool for crimping the collars as I described in my Water Accumulator submission. Actually, the accumulator I showed there is now being used in this potty water flush system.

The intake of the Shurflo pump has a male fitting to connect to a 10 foot length of regular garden hose. The other end of the hose is connected to the water hose size adapter on the end of the main dump outlet (photo #4). If your RV has the solid cap it can be easily exchanged for one with the garden hose connection. Most any RV parts and accessory store carries the caps with the garden hose outlet. The bath water tank dump valve is left open so water is present at the outlet.

It worked great! Yes, it may be overkill, but if you enjoy dreaming up and making mods to your RV this one is pretty cool. If you don’t like doing unnecessary mods, get yourself a bucket.

ModMyRV recommends these parts for this mod:
SHURflo 2088-422-444 Classic 2.8 GPM Pump
SHURflo In-Line Filter - 1/2″ Barb Input x 1/2″FPT Output
Valterra Products, Inc. F02-3106BK Black Bulk EZ Coupler Valve Cap with Handle


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