Adding an Additional Check Valve Between Fresh Water Tank and Shurflo 4008 Water Pump

Updated 09/02/2025 | Published 08/04/2025

Products Featured in This Question

B&B RV In-Line Check Valve - Black

(5)

$8.79

Camco RV Fresh Water System Backflow Preventer - 1/2" Diameter NPT - Brass

(37)

$11.17

Question:

I would like to add a 1/2inch inline check valve to the water line between the fresh water tank and my Shurflo 4008 water pump as a backup to the integral check valve in the pump. The ports on the pump are not tapered threads. I think they are probably NPSM threads. All of the inline check valves I have been able to find, including those on etrailer.com, have tapered threads. Are there check valves available that are compatible with the thread on the Shurflo pump?

asked by: Peter

Expert Reply:

Hey Peter, thanks for reaching out!

It looks like all of the check valves we carry use the NPT type of tapered threads, but we still might be able to make this work.

If you're able to modify your water line at all, you can then install a check valve like the B&B # BM38GR or the Camco # CAM23303 depending on what fittings you use. This will add more potential fail points to the water system, but it's going to be your best bet to adding another check valve when your water pump has a unique thread style.

What kind of water line do you have between the fresh water tank and your pump?

expert reply by: Jon G

Jon G.

9/2/2025

Hey Peter, did you find a way to modify your water line to install the check valve? I'm asking because your experience could help others facing the same issue with unique thread styles on their water pumps.

Peter

9/2/2025

In researching check valves, I learned that check valves should be installed five pipe diameters away from any fittings both before and after the check valves. With that in mind, I bought two 1/2” NPT x 1/2” barbed adapters. I installed the adapters onto the check valve, cut the water line and installed the check valve into the water line 3” from the pump using 1/2” pipe clamps to secure the check valve into the line.