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Frequent Asked Questions

FAQ: Frequently Asked Questions Answer

Flushing with Gray Water?

phred Tinseth © 1999-2002 Reproduction permitted

Flushing with Gray Water -- For those who know what they're doing

Just some notes.

  • I used gray water for flushing on boats (and later in travel trailer).
  • Relatively simple on boat since had access to top of gray tank. Some RVs have access also if lucky.
  • Some marine terms/equipment referred to here. If you're not familiar with them get copy (free) of "West Marine" catalog. (www.westmarine.com). Excellent, descriptive reference. Useful for many RV things. Variety of hatches, pumps, etc. Once you know what to look for, can shop around salvage yards.
  • On boat: I cut hole in top of tank to fit "Deck Hatch/Plate." (Two-piece waterproof access hatch.) Comes in various sizes. Has flange and hatch insert. Hatch flange made to be screwed to decking, but can be cemented to water tank. Inserts come in screw-in or cam type. Have "O" ring seals.
  • Inserted small, submersible, 12V bilge pump into tank. Since not trying to prevent sinking, used smallest, cheapest pump. 12V wiring and tubing easily sealed through small hole in hatch (why cam type is better than screw in).
  • Ran 12V wiring and 3/8" flex vinyl tubing to toilet area. Attached electric switch and kitchen sink spray hose.
  • Have seen people attach directly to toilet input, but not always too swell. Can be messy as particles plug small holes in toilet and limits flexibility.
  • Have seen people use "tees" and valves so can switch from fresh water to gray. Not too swell. Requires elaborate use of expensive check valves and vacuum breakers and fresh can still get contaminated.
  • Above is basic, crude system.

In RV, used a variety of pumps. Old style RV pump, (big diaphragm in can with exterior motor on top turning eccentric arm) worked best. Was bought at flea market for next to nothing. Had pressure switch, so just had to run water line to toilet area and manual switch to any convenient place (near fresh water pump switch so was easily reminded to turn them off when leaving RV). In use at toilet, just had to point sprayer and squeeze trigger.

  • At tank, since just need about 1/2" fittings, can sometimes attach to an existing, extra fitting (if there are any). Go through side, near but not at bottom (where heavy crud collects).
  • RV and marine stores have threaded fittings that can be cemented to tank. Better is a "compression-type" fitting (plastic with big vinyl ring that works similar to small brass compression fittings). Costs more, but is more reliable and flexible.
  • If you draw water from about 3 or 4" up from bottom of tank, you won't get much crud.
  • RV and marine stores have a fitting that is built like a threaded bushing. Usually 3/4" outside thread by 1/2" inside thread. Stuck on the end that goes into the tank is a tubular screen of stainless steel about 2" long. If your initial access to tank mentioned above is 3/4" and you screw the screen bushing into that, then you can attach standard 1/2" RV hose and fittings to connect the pump. You'll get very little crud in pump. Once or twice a year, when gray water level is below the tank fitting, it can be unscrewed and cleaned.

Reminders And Odds & Ends

  • Neither black or gray water should stink IF you treat them properly. See elsewhere in this poopsheet. You do NOT just cram chemicals in a tank. You use "biological" agents that decompose waste.
  • Various pumps: The old timer mentioned above is reliable and easy to repair. I have also used a macerator for this (since I had an extra). I've seen people use rotary drill pumps (that cost as little as $4 but wear out early). About 10 years ago, you could easily find a "tiny" macerator in surplus stores. These cost about $15 and were from some ill-advised venture that incorporated them into the bottom of some camper or marine toilet. If you find one, they work great (I had one). There are all sorts of fountain pumps, trash pumps and similar. Best way to view the variety available is check the "W.W. Grainger" catalog available at about any hardware store. Check Yellow Pages for things like Industrial Supplies, Surplus, Salvage, etc.
  • The odd fittings I mentioned aren't really odd. Good RV stores will have them in bins and you can just poke around and find them. Camping World has them, but you have to go to the special parts counter and try to explain what you want to some numb nut -- not much fun.
  • Deck hatches are good for lots of things. I have one on top of my fresh water tank. Above the low-end output, it allows me to clean the bottom of the tank (that always holds an inch of water and crud when drained). I have another through the floor directly above the 65 gal fuel tank. By carefully measuring, I got it directly above the fuel pump/pick up/gauge unit that drops down into the tank. (Why drain and drop a tank if you don't have to?)

Sanidumps.com's Instructions on How to Empty Your RV Holding Tanks

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