I have a 2007 Recon ZX 36V Toyhauler. I am trying to figure out which of the 3 dump valves are which, black-grey1-grey2. I haven't been able to find any schematics or pictures to help me. HELP

If you had both tank dump valves opened and the same time, raising the hose above the top of the tanks could allow liquids to mix. Gray water can smell as bad as the black tank, so you can't depend on odor. Best practice is to dump the black tank first, close the valve, then use the gray tank to flush the hose out.

At the Dump Valves, Large and Small Tubes, open the one for Grey Water only which is usually the small tube. Pull the Handle of that one at a Dump Station of course. Grey water should also not be dumped anywhere else but a Dump Station.

the grey water is your shower and sink drain tank. the black water is your... you know. the two combine to the dump that's held together with a bypass for grey water to flow into the black tank and vice versa so you can flush the black tank further. all of this comes out the end into your dump out for black and grey. If your talking about white water (potable) holding tank, filling this drains through the use of it, run the shower outside or hold flush down until it drains. otherwise. the hotwater tank will drain with the anode when you regularly change that once a year as directed by people who camp once a year - change that anode -

Need a new valve!

If they are blade valves (a T-handle that you pull out and push in) then they are probably your black water (the largest diameter one) and grey water. The third is probably a 2nd black water tank if you have a bath and a half. They often have a separate black water tank.

U SHOULD HAVE A BLACK TANK AND A GRAY. TOWARDS THE BACK WERE U HOOK UP THE HOSE FOR DUMPING U WILL SEE TWO LEVERS ONE IS FOR BLACK ONE IS FOR GRAY. AND IF UR TALKING ABOUT FRESH HOLDING TANK LOOK UNDER NEATH AND U SHOULD SEE A PLASTIC NOSEL WITH A TURN VALVE LIKE WHAT BOX WINE HAS TO PURE A GLASS

There will be a couple of valves located on the drivers side of the unit. One will be a wide valve, 3", and the other will be a narrow valve, 1-1/2". The wide valve is the black water dump valve. Make sure you are connected to a dump station, open the valve and allow the waste to flow out. You can purchase a tank flush wand that will aid in the flushing of the tank. You connect it to a water hose and insert it into the tank through the toilet and flush the tank with the valve open.

On some later model Montana 5th wheels, there are actually three holding tanks which will eventually require draining. (two grey tanks, 1 for the kitchen sink(s) and 1 for the bath tub & bathroom sink, and one black tank, obviously the toilet...) The two most used drain valves (1 black & 1 grey) are together in the docking station area where the city water supply is hooked up, the other (kitchen sink) is at the left rear of the coach behind the farthest rear wheel along the frame. (That is where "Keystone" installed the grey tank for the galley, or kitchen if you prefer.)
If certain it is the black tank which won't dump when the black tank valve is pulled, there is a restriction before the valve (or the valve itself is not opening hence a broken cable to the valve?) One might try "snaking" up into the sewer line, measuring the distance from the outlet to the valve location, assuring it is either open or closed. Once that has been determined, you will at that point have to remove the sewer line at the valve for repair. Be sure to wear latex gloves and eye protection and have a drain pan or bucket handy for spillage which can be collected and dumped down your home toilet or outside sewer clean out if you know its location.

Fresh water holding tank will have a single 1/2" line hanging down under the trailer. It will have either a cap or a valve. To drain open the valve or remove the cap. For gray water and black water you must be connected to an approved dump site with an approved RV sewer line. Open the 3" valve first and allow the black tank to drain then open the 1-1/2" valve to drain the gray water. This will flush the sewer line as well.

Should be readily visible underneath the unit. Begin your search near the Black Water tank, which is the one most directly connected to the sewage release valve where you hook the dump hose. Usually, Grey Water dumps through the same hose via a second dump valve.