An RV's black and gray holding tanks generally drain through their own valves before the waste reaches a shared outlet and sewer hose. Because valve bodies, assembled valves, bayonet fittings and rinse accessories do different jobs, they should be identified separately. This RV holding-tank system diagram shows the functional flow and connects you to exact waste valves, hose fittings and tank-monitoring products in NewRVParts.
From black and gray tanks to the sewer connection
The two tank branches shown below are separate until they reach an appropriate outlet junction. Individual RVs may have additional tanks, different valve diameters or a second outlet. Always identify the actual assembly before ordering replacement parts.
Black-water branch
The tank-level probe senses liquid level; it is not part of the discharge piping.
Gray-water branch
Valve size and exact connection type depend on the particular trailer or motorhome.
The dump hose must be securely connected and routed to the approved disposal point before operating the tank valves. Keep the waste system separate from drinking-water hoses and plumbing.
Choose the fitting style before choosing the valve
A socket connection intended to receive the corresponding pipe or spigot. A hub-to-hub valve and a hub-to-spigot valve are different complete assemblies.
A pipe-sized male end that enters the matching socket. Compare both sides of the existing valve, not just the nominal 3-inch or 1½-inch size.
A twist-lock waste outlet or hose connection. A capped bayonet valve such as T50 is not the same as a bare hub/spigot valve such as T40.
What each holding-tank component does
| Part role | Example | How to identify it |
|---|---|---|
| Waste isolation valve | T40 | 3-inch manual hub-to-spigot assembly; two different fitting ends |
| Smaller branch valve | T1001 | 1½-inch manual spigot-to-hub assembly |
| Capped termination valve | T50 | 3-inch hub inlet with a capped bayonet waste outlet |
| Remote control | TC372 | 3-inch valve operated by a separate 72-inch cable |
| Sewer discharge fitting | Camco 39736 | 90° elbow and 4-in-1 dump-station adapter |
| Rinsing attachment | Camco 39072 | Clear in-line flushing accessory, not an ordinary dump valve |
| Holding tank level sensing | T21301VP | Black-water probe set for compatible tank monitors; not a drain fitting |
A transparent rinse fitting is an optional cleaning accessory used with the correct sewer connection; it does not replace a waste gate valve. If using a flushing hose, follow the manufacturer’s backflow-prevention instructions and avoid cross-contaminating potable-water equipment.
Find the matching waste-system parts
Each card links to the exact NewRVParts product with its existing catalog image. Check dimensions, mating fittings and current warehouse availability on the listing. NewRVParts ships from supplier warehouses; items are not available for in-person viewing or pickup.
Toilet and macerator parts references
Toilet service parts and waste macerator equipment follow different replacement paths. Gravity-flush toilets, permanently installed macerators and portable dump pumps should be identified by their original model number before selecting parts.
Detailed waste-valve and tank service references
Manufacturer connection and service references
Valterra provides part-numbered references for the T40 3-inch hub/spigot valve, T1001 1½-inch valve and black-tank Horst level-probe design. Camco documents the 39736 90° sewer elbow and 4-in-1 adapter. Follow the exact component installation instructions and RV manufacturer plumbing information for connections, seals and clearances.