Tecreddy RV Toilet Flush Ball Seal Replacement for Dometic 300/310/320 - 2-Pack Durable Rubber Gaskets

Tecreddy’s two-pack RV toilet flush ball seals replace Dometic part 385311658 for 300, 310 and 320 series toilets, restoring a reliable, watertight flush seal.

If your RV toilet is leaking, not holding water, or feels loose around the flush ball, a worn gasket is often the culprit. These replacement seals are molded from a durable rubber compound to match the original dimensions for a snug fit and extended service life. They’re sold as a value two-pack so you have a spare on hand for future maintenance.

How will this seal fix a leaking or weak flush?

The flush ball seal creates the watertight barrier between the bowl and the flush valve. When the original rubber hardens, cracks, or becomes misshapen, water escapes and the toilet won’t hold a proper water level. Replacing the gasket restores the intended seal and improves the toilet’s performance without replacing the entire unit.

• Direct fit for Dometic 300, 310, 320, 400, 410, 420 series toilets
• Matches OEM dimensions for a consistent seal
• Stops common leaks caused by hardened or torn gaskets

Is it difficult to install the new flush ball seals?

Installation is designed to be quick and tool-free in most cases. You generally pop the old seal out and press the new one into place with the marked side facing up, no disassembly of the toilet required. A properly seated gasket should sit flush with the valve opening to ensure full sealing.

• Typical install time: a few minutes per seal
• No special tools needed for standard Dometic toilets
• Marked side indicates correct orientation during installation

What size are these gaskets and which models do they fit?

Each gasket measures approximately 4 inches outer diameter and 2.75 inches inner diameter, matching the original OEM sizing for compatible Dometic models. These seals replace part number 385311658 and are not compatible with models such as the 210 or 510 series or other unlisted toilets.

• Outer diameter: 4 inches; inner diameter: 2.75 inches
• Replaces Dometic part number 385311658
• Compatible: Dometic 300, 310, 320, 400, 410, 420 (not for 210, 510)

Why choose a two-pack rather than a single seal?

Buying a pair gives you immediate replacement for one failing seal and a spare for future wear, saving both time and money. Rubber seals degrade over years of use and exposure to chemicals, so having a backup reduces downtime and the need for repeat orders.

• Cost-effective compared with individual seal purchases or service calls
• Keeps a spare on hand for seasonal maintenance
• Factory-molded from the original pattern for consistent fit

Who this is for: RV owners and fleet managers with Dometic 300/310/320 (and select 400-series) toilets who need a reliable, low-cost repair option. Ideal for DIY maintenance, rental operators, and anyone looking to stop leaks and restore flush performance without replacing the whole toilet. If you’re unsure about fit, check your toilet’s model number and part reference before ordering, and contact Tecreddy customer service for assistance.