Hi Yvon;

In Fluid Control systems these are known as "Check Valves" their

purpose

is to

hold or prevent the fluid on reverse flow. In other words once the

fluid

flows

thru the valve it can not go back through it. So in order to answer your
question of whether they are necessary or not a sketch of your fuel

system

(schematic) is needed.
                                                    Butch

  I am currently working on my fuel system and the same thing crossed my

mind

as the positive

displacement pumps wont allow to backup through them I don't think they

would

be needed.

 I am running two pumps parallel with a pickup in the tank for each pump

and

the pumps tee

together into one line that goes to the carb.
 Ken Welter

********************************************************************************

Hi Ken,......What type of pumps are these, obviously yours are low pressure
since you're feeding a carburetor, how much pressure are they capable of
developing?.....Are they piston, diaphragm, vane, gear?...where are your check
valves plumbed in.....are they in the two (2) suction lines?.........Is there
one on the tee'd outlet to the carb?
                                                       Butch

 
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