Primary Fuel Filter Vertical Separation Question

[Cheechako]

Many boats have a fuel filter in the engine space well above the tank. Maybe 3 ft? Other boats have it below the floorboards but still at about tank top level.
I would think it's fine, but the electric prime/backup pump is a nice option, especially with a 3 way valve to bypass the electric pump when desired. (with yours at 5 ft lift will the electric pump restrict making the lift even more difficult when the electric pump is not on?)

[parkstone bay]

Oh dear, some people seem to have forgotten their basic physics! Once the system is primed, the distance the lift pump has to handle is the vertical separation between the fuel in the tank, and the engine - it doesn't matter to what height (or depth) the intervening pipework is routed.
I put on a primary filter with a bulb priming pump, I'd have thought it'd handle a 3 ft head.
As regards the original question about check valves, etc - why? If the pipework is in good condition, it'll last the life of the engine; if you're concerned about a rupture somewhere, then that could happen with a straight pipe.

[nofacey]

Another vote for adding an electric lift pump ahead of filter - solves a host of issues, can be a god send in some instances.
I use this one https://www.amazon.ca/CarBole-Univer...s%2C254&sr=8-6

[Dalestr]

Originally Posted by nofacey

Another vote for adding an electric lift pump ahead of filter - solves a host of issues, can be a god send in some instances.
I use this one https://www.amazon.ca/CarBole-Univer...s%2C254&sr=8-6

I love electric fuel pumps too and swapped my Yanmar's (2GM20F) lift pump for a Facet electric (cube style) pump, the lowest pressure unit. It sure beats working the pump lever when bleeding points downstream but I did it mainly for fear of the diaphragm leaking fuel to the crankcase. The old pump is now my spare, stowed away.
There is a fair complexity to electric pumps besides the need to power them. Pressure ratings, valving systems, lifting head, etc. Take a look at the Pegasus Auto Racing site here https://www.pegasusautoracing.com/ad...ryID=FUELPUMPS
to see the great variety of pump offerings from Purolator-Facet. Most are UL Marine Listed. Some have free flow, some with a stop valve, and some act as a check valve when deenergized.

The generic Amazon pump nofacey links us to includes scant info about these parameters and the pump includes a basic inline filter. You want that filter upstream to prevent grit affecting it. The Facet Gold-Flo pumps do include an integral strainer in the base so those could be used upstream but normally aren't because it can collect water and then rust. By their impulse nature, electric pumps also tend to emulsify water in the fuel, unlike diaphragm pumps, but that's another reason to have the primary upstream of them. Of course, if you have the space and the need you can run bypass plumbing around a pump that is used in an auxiliary or emergency role. That's not really a lift pump though. It's a great idea for a larger boat but it is a bit much for a smaller one.
One other method to allow air bleeding (or filling) at an elevated primary filter is to mildly pressurize the tank. Using a pool toy air pump (12V) with 0.3 psi output, you can raise the diesel head quite a bit. Pascals Principle applies and is based on the relative surface area of the fuel tank section vs. the fuel line section. I've been using a dinghy foot pump to do this lately. Still, it's hard to beat the simplicity of the bulb pump and I may revert back to that method for expediency. They don't work quite as well in cold conditions below say, 35F as the polymer stiffens up.