22RKHL Forest River Water Tank Diagram: Installation Setup 2026
Under the 22RKHL Forest River Heritage Glen Hyper Lyte, the freshwater tank is positioned forward over the front axle. The primary gray tank for the kitchen sink drain assembly sits mid-ship, while the black tank and secondary gray tank reside directly beneath the bathroom footprint along the driver-side frame rail.
📌 Key Takeaways
- Freshwater tank is mounted near the axle assembly to maintain proper tongue weight balance.
- Kitchen sink waste routes through a 1.5-inch tailpiece and P-trap into the dedicated rear gray tank.
- Always depressurize system and drain all waste tanks before unscrewing belly pan panels.
- Slow sink or shower drainage is frequently caused by a clogged roof vent pipe rather than full tanks.
- P-trap and valve repairs are DIY-friendly, but cracked structural tank mounts require professional service.
Navigating the underbelly plumbing layout of a Forest River Heritage Glen Hyper Lyte 22RKHL requires a clear understanding of where each holding tank rests between the I-beam frame rails. Because Forest River encloses the underbelly with thermo-foil insulation and corrugated Coroplast panels, visual inspection without documentation can be difficult. This guide provides the exact component layout, plumbing schematics, and frame reference points for the 22RKHL floorplan. Using OEM structural specs, you can pinpoint your fresh, gray, and black water tanks along with their associated drain assembly, P-trap connections, and stack venting routes without blindly tearing down belly panels.
22RKHL Forest River Heritage Glen Hyper Lyte Water Tank Diagrams and Component Breakdown
The 22RKHL model utilizes a specialized rear-kitchen floorplan layout that splits gray water management across two separate holding tanks. Standard manufacturer specifications dictate that tank placement is optimized for tongue weight distribution across the dual-axle system. As shown in the diagram above, three primary tanks and one secondary holding vessel are secured within the floor frame crossmembers using heavy-duty galvanized steel angle iron hangers.
Fresh Water Tank and Pump Suction Line Positioning
The fresh water holding tank (49-gallon capacity) is located forward of the front axle, positioned between crossmembers 2 and 4 directly beneath the master bedroom floor. It sits elevated above the bottom frame flange to protect the tank structure. A 1/2-inch PEX suction line runs from the bottom side port of this tank directly to the 12V water pump mounted behind the driver-side pass-through storage partition wall. Low-point drain valves extend through the belly pan immediately behind the front crossmember. For detailed wiring schematics regarding the pump circuit, consult our guide on RV fresh water pump wiring.
Rear Kitchen Galley Gray Tank and Drain Assembly Layout
Because the 22RKHL features a rear kitchen, the primary galley gray tank (30-gallon capacity) is suspended at the extreme rear of the chassis, occupying the bay between the rear bumper and the rear axle assembly. The kitchen sink drains through a 1.5-inch sink tailpiece linked by a threaded slip joint to a removable PVC or ABS P-trap. The waste pipe passes through the floor deck, connecting directly to the top inlet of the galley tank. An air admittance valve (AAV valve) is plumbed into the upper vertical riser beneath the kitchen counter to prevent siphonage without needing a direct roof penetration over the galley area.
Mid-Ship Black and Bathroom Gray Holding Tanks
The toilet and bathroom sink/shower utilize a dual-tank enclosure mid-ship, mounted directly above the axle cluster. The black water tank (30-gallon capacity) sits directly below the toilet flange to allow a straight vertical drop. The bathroom gray tank (30-gallon capacity) sits adjacent to the black tank, receiving drainage from the shower stall low-profile P-trap and bathroom sink drain assembly. Both tanks feed into a unified termination manifold behind the driver-side skirt board.
| Tank Type | Location Landmark | Capacity / Specs | Plumbing Connection Type |
|---|---|---|---|
| Fresh Water Tank | Forward of Front Axle (Bay 2-4) | 49 Gal / Rotomolded PE | 1/2″ PEX Supply / 1-1/4″ Gravity Fill |
| Galley Gray Tank | Aft Frame Bay (Behind Rear Axle) | 30 Gal / Low-Profile ABS | 1.5″ ABS / PVC Drain Assembly with AAV Valve |
| Bathroom Gray Tank | Mid-Ship (Directly Over Axles) | 30 Gal / Thermoformed ABS | 1.5″ Hub x Slip Joint P-Trap Line |
| Black Water Tank | Mid-Ship (Directly Under Toilet Flange) | 30 Gal / Sloped-Bottom ABS | 3″ Vertical Closet Flange & Vent Pipe Stack |
According to Forest River OEM schematics, all waste tanks on the Hyper Lyte series are constructed from 0.187-inch nominal wall thickness ABS plastic. Frame crossmembers use 12-gauge cold-rolled steel channels spaced at 24-inch centers. Drain lines maintain a mandatory 1/4-inch per foot slope toward termination valves.
Locating Water Tanks Under Your 22RKHL Forest River Heritage Glen Hyper Lyte Step-by-Step
To verify tank locations and inspect your plumbing lines on a 22RKHL without completely stripping the underbelly insulation, follow this step-by-step diagnostic sequence using frame landmarks and access points.
Step 1: Removing Underbelly Coroplast and Insulation Barriers
Position the trailer on level concrete and drop the corner stabilizer jacks. Locate the steel self-tapping screws securing the corrugated plastic underbelly panel to the bottom frame flange on the off-door (driver) side. Remove the screws starting 3 feet behind the rear axle to access the galley tank bay, or forward of the front axle for the fresh water tank. Pull the flexible panel down gently to expose the radiant foil barrier and fiberglass batts without tearing the material. If retrofitting or replacing damaged vessels, refer to our comprehensive gray water holding tank replacement guide.
Step 2: Tracing the Main Drain Assembly and P-Trap Lines
Locate the main sewer termination outlet under the driver-side frame rail. Trace the 3-inch black ABS pipe backward to locate the mid-ship black tank. Follow the secondary 1.5-inch ABS line running rearward along the inner web of the I-beam to locate the galley tank. Check where the sink tailpiece drops down from the cabinet base; inspect the 1.5-inch slip joint compression nut and glue-joint connections to ensure frame flex has not stressed the PVC pipe fittings.
RVs do not utilize high-power mechanical residential garbage disposal units due to power constraints and tank solid accumulation. Instead, the 22RKHL rear sink relies entirely on a smooth 1.5-inch smooth-bore drain assembly and slip joint P-trap to prevent solids from clogging the galley tank inlet port.
Step 3: Mapping Vent Pipes and Roof Stack Connections
Each holding tank must vent displacement air to prevent vacuum locks. The mid-ship black tank uses a rigid 1.5-inch vertical vent pipe running through the bathroom partition wall, terminating through the roof vent cap. The galley gray tank uses a dual-venting system: a main roof stack rising behind the refrigerator cavity and an auxiliary AAV valve (air admittance valve) threaded onto a riser behind the sink drawer stack. Verify that the vent pipe rubber grommets on the top of the tanks are properly sealed with butyl tape or urethane adhesive.
Troubleshooting Drain Assembly Leaks, P-Trap Fittings, and Tank Venting
Plumbing failures within an enclosed underbelly often manifest as hidden leaks or sluggish drainage. Use the following diagnostic protocol to identify issues in your 22RKHL system.
Diagnosing Vent Pipe Obstructions and AAV Valve Failures
If the rear kitchen sink gurgles or drains slowly despite an empty galley tank, the mechanical seal inside the inline AAV valve under the counter has likely failed or stuck closed. Unscrew the AAV valve from its threaded PVC adapter and check the internal diaphragm. If sewer gas odor is detected inside the rear galley cabinets, the valve diaphragm is stuck open, allowing gray tank fumes to escape inside the coach. Replace it with a standard 1.5-inch NPT air admittance valve.
Never apply solvent-based cleaners or high-pressure air directly down an RV tailpiece or drain assembly. Excess pressure can blow off under-floor slip joints or crack rigid ABS pipe joints inside the enclosed underbelly, leading to concealed rot. If repairing damaged belly sheeting, see our instructions on underbelly insulation repair methods.
Fixing Slip Joint Seeps and PVC Drain Assembly Cracks
Vibration from highway travel routinely loosens threaded slip joint nuts under the sink tailpiece. Inspect the rubber washer inside the slip nut for distortion. If fluid leaks originate beneath the floor, inspect the joint where the 1.5-inch schedule 40 ABS drain line enters the rubber tank grommet. Frame twisting can pull non-flexible PVC pipe transitions out of alignment; replace rigid sections with flexible marine-grade wire-reinforced hose if chronic stress cracking occurs.
Where Can I Get a Diagram Showing Water Tank Locations Under My 22Rkhl Forest River Heritage Glen Hyper Lyte: FAQ
How can I request official Forest River OEM schematic diagrams for my 22RKHL?
Official structural and plumbing schematics can be requested directly through Forest River Owner Relations by providing your 17-digit Vehicle Identification Number (VIN). Because Forest River updates mid-model year production runs, referencing your specific VIN ensures you receive the exact tank layout diagram corresponding to your chassis build date.
Why does my 22RKHL have two separate gray water tank drains?
Due to the distance between the rear kitchen floorplan layout and the mid-ship bathroom, running a single sloped 1.5-inch drain pipe across the entire length of the chassis would reduce ground clearance. Forest River utilizes two dedicated 30-gallon gray tanks: one for the galley drain assembly and one for the shower/bathroom sink assembly, each connecting to individual or manifolded termination valves.
Where is the air admittance valve (AAV valve) located on the rear kitchen sink?
The AAV valve on the 22RKHL is located inside the rear kitchen sink cabinet, mounted vertically on a pipe riser positioned above the height of the sink P-trap weir. It sits behind the top drawer slide rail and can be hand-unscrewed for inspection or replacement without tools.
Can I replace damaged ABS drain pipes under the floor with standard schedule 40 PVC?
Yes, but you must use transition cement designed specifically to bond ABS to PVC (typically green in color). Standard clear PVC medium cement will not create a molecular weld between black ABS and white PVC fittings, which can result in joint separation due to road vibration.
