The best grey water holding tank depends on the required capacity, available installation space, and outlet arrangement. The Class A Customs 32- and 34-gallon tanks are waste-water-only options for RVs and campers; the T-4000 offers 40 gallons and can also hold fresh water. A 16-gallon waste tank may suit a smaller installation, while the 1,000-gallon vertical tank is for bulk water storage—not a clearly specified grey-water waste application.
| Product | Capacity | Best suited for |
|---|---|---|
| Class A Customs WT-3418 | 34 gallons | More capacity in a similar waste-tank category |
| Class A Customs WT-3232 | 32 gallons | RV and camper waste-water systems |
| Class A Customs T-4000 | 40 gallons | Fresh or grey water storage |
| Class A Customs WT-1653 | 16 gallons | Smaller waste-water installations |
| Elkhart Plastics vertical tank | 1,000 gallons | Bulk water storage, not specified for grey waste |
Class A Customs WT-3418 34-Gallon Tank
This 34-gallon tank is made from medium-density polyethylene and is listed for waste or grey water use in RVs, campers, trailers, motorhomes, and tiny houses. It has a fixed 1.5-inch ABS female pipe outlet. Choose it if you need a dedicated waste tank and its dimensions fit your installation; it holds two gallons more than the WT-3232.
Installation note: The outlet cannot be moved, and the inlet and vent must be installed by the user. Hardware and connecting pipe are not included. The tank must be vented and must not be pressurized.
Class A Customs WT-3232 32-Gallon Tank
The WT-3232 is a 32-gallon MDPE waste-water tank for RVs, campers, trailers, motorhomes, and tiny houses. Its 1.5-inch ABS female outlet is installed and cannot be repositioned. It is best for buyers seeking a dedicated grey-water tank with slightly less capacity than the WT-3418.
Installation note: Inlet and vent placement is up to the installer, and the necessary hardware is not included. The listing says a dump valve should connect through PVC or ABS piping rather than directly to the tank fitting. Do not overtighten fittings or pressurize the tank.
Class A Customs T-4000 40-Gallon Tank
The T-4000 holds 40 gallons and is described as suitable for fresh or grey water. Its listed dimensions are 39.5 by 13 by 18 inches, excluding fittings, and it can sit on any side. This is the best option in this selection for buyers who want greater capacity and may also use the tank for fresh-water storage.
Installation note: The tank has two 1.5-inch female NPT fittings and two open 0.5-inch female NPT fittings. The manufacturer cautions against overtightening and recommends plastic connecting fittings because metal can damage the threads. Confirm the fittings and layout suit your system.
Class A Customs WT-1653 16-Gallon Tank
This compact 16-gallon MDPE tank is listed for waste or grey water use in RVs, campers, trailers, motorhomes, and tiny houses. It has a fixed 3-inch ABS female outlet. It is best for an installation where a smaller holding capacity is useful and the 3-inch outlet matches the planned plumbing.
Installation note: Inlet and vent placement, hardware, and connecting parts are not included. The listing has conflicting outlet-related wording about dump-valve connections, so confirm the required pipe and valve arrangement before purchase. The tank must be vented and not pressurized.
Elkhart Plastics 1,000-Gallon Vertical Tank
This UV-resistant HDPE tank is described for bulk water, well water, rainwater, and other water-storage uses. It has two 16-inch manway lids, a 1.5-inch fitting at the top, and 2-inch fittings at the bottom. It is included as a large-volume storage comparison, not as a recommended grey-water waste tank: the supplied details do not specify grey wastewater use.
Choose it only when the intended application is water storage and its large vertical format and fittings meet the project requirements. Do not assume that drinking-water materials make it appropriate for wastewater.
Buying Guide: How to Choose a Grey Water Holding Tank
How much capacity do you need?
Compare the tank’s stated gallon capacity with your available space and expected water use. The listed RV waste tanks range from 16 to 34 gallons, while the T-4000 holds 40 gallons. A larger tank can reduce how often it needs emptying, but it also requires room and suitable support. Verify product dimensions before planning an installation.
Does the outlet match your plumbing?
Check the outlet diameter, fitting type, and fixed location against your planned pipework. The WT-3232 and WT-3418 have fixed 1.5-inch ABS female outlets; the WT-1653 has a 3-inch outlet. The T-4000 uses NPT fittings. Do not assume a dump valve connects directly: follow the product’s plumbing instructions and account for any additional pipe or fittings.
Is the tank intended for grey water?
Use a product whose listed use supports the intended application. The WT-3232, WT-3418, and WT-1653 are described for waste or grey water, while the T-4000 is listed for fresh or grey water. The 1,000-gallon model is described for water storage, not grey wastewater.
What installation details matter?
Plan for venting, inlet placement, secure mounting, and compatible connections. The Class A Customs waste tanks require user-installed inlet and vent openings, and their listings state that hardware is not included. Avoid overtightening fittings. Never pressurize a tank unless its manufacturer explicitly specifies that use.
Frequently Asked Questions
Can a fresh-water tank hold grey water?
Only when the product information explicitly permits grey-water use. The T-4000 is listed for fresh or grey water; do not assume other potable-water tanks are suitable for wastewater.
Do these tanks include an inlet and vent?
The listed Class A Customs waste tanks come with an outlet, while the user determines and installs inlet and vent locations. Their listings state that hardware is not included.
Can a dump valve attach directly to a 1.5-inch outlet?
The WT-3232 and WT-3418 listings say to run PVC or ABS pipe from the outlet and add the dump valve to that piping, rather than attach the valve directly.
Can these waste tanks be pressurized?
No. The Class A Customs waste-tank listings explicitly warn not to pressurize the tanks and state that they must be vented.