Red Sea MAX E/S/Reefer Downflow Valve Diaphragm
Water type
Marine
Fits
Red Sea MAX E-series, Red Sea MAX S-series, Red Sea REEFER systems
Part no.
R40370-V4
Red Sea MAX E/S/Reefer Downflow Valve Diaphragm
Genuine Red Sea spare — keep your downflow valve sealing properly. This is the replacement diaphragm for the downflow valve fitted to Red Sea MAX E, MAX S and REEFER systems — genuine Red Sea part R40370-V4.
Key features
- Genuine Red Sea replacement — the small rubber diaphragm that seals and regulates the downflow valve.
- Restores proper valve regulation — a stiffened or split diaphragm is a common cause of a downflow valve that won't hold a stable level or runs noisy.
- Simple DIY swap — no need to replace the entire valve body.
Will it fit my tank?
Red Sea part R40370-V4 is used in the downflow valve across the MAX E-series, MAX S-series and REEFER ranges. Red Sea's specific parts diagrams (by exact model and generation) weren't accessible from the manufacturer's site at the time this page was written — if you're not certain of your exact model and generation, send it to us before ordering and we'll confirm against Red Sea's parts records.
Suitable for, and not suitable for
- Suitable for: the downflow valve assembly on Red Sea MAX and REEFER systems.
- Not suitable for: other brands' overflow valves — it's a direct-fit Red Sea part, not a generic diaphragm.
Fitting notes
The downflow valve assembly is removed from the valve body to access the diaphragm — Red Sea's cleaning and adjustment guide for the downflow valve covers the same disassembly steps. Rubber parts age even when they still look intact, so replacing the diaphragm during routine maintenance is worth doing ahead of a failure rather than after a noisy overflow shows up.
Warranty and delivery
Covered by the manufacturer's standard warranty against defects, in addition to your rights under Australian Consumer Law. Standard shipping across Australia.
Common questions
How do I know if my diaphragm needs replacing?
A downflow valve that won't hold a stable water level, needs constant micro-adjustment, or has become noisy are the usual signs — though a stuck or dirty valve body can cause the same symptoms, so it's worth cleaning the valve first.
Do I need to remove the whole valve to fit this?
Yes — the valve assembly comes out of the body to access the diaphragm, the same disassembly Red Sea describes for cleaning and adjusting the valve.
Not sure if this fits my system — what should I do?
Send us your exact model and generation before ordering and we'll confirm fitment against Red Sea's parts records.
