Raypak Genuine OEM Bypass Dam/Shaft, 006717F

This is the genuine Raypak 006717F bypass dam and shaft, molded in Capron and supplied as one part. Raypak lists it for the R185A, R265A, R335A and R405A pool heaters.

What the bypass does

A gas heater does not want every gallon the pump can push routed through the heat exchanger. The internal bypass splits the flow, sending part of it through the exchanger and part of it around, so the exchanger sees the flow rate it was designed for regardless of what the pump is doing. The dam is the element that sets that split, and the shaft is what it pivots on.

When it needs replacing

Plastic parts inside a heater live a hard life: heat cycling, chlorinated water and whatever mineral content the fill water carries. A dam that has worn, cracked or lost its shape stops metering flow correctly, and the heater then either short cycles on high limit or runs a poor temperature rise.

While you are in there

The bypass valve and its spring sit alongside this part and wear at a similar rate. It is worth inspecting them once the assembly is open, since the labor is the same either way.