Add tank, would I add a lift pump?

[Mach_cat]

Under my salon, I have an extra unused fiber glass tank. It will hold roughly 70gallons. This tank currently has only a spot for one hose. No inlet and the one hose has never been connected to anything. So I am thinking this would make a nice fuel tank that I can run fuel to from the other 2 tanks. Polishing the fuel before putting in this tank.
Now I assume this would need 2 pumps. One to run the fuel from the tanks through the polishing filters then to the tank. And another to go from this tank back forward to my racors then to the engine. The racors would maybe 10-15 feet from the tank. (my engine is located up near the helm and the racors are forward of that.) the 2 tanks are higher than the racors so no lift pumps just the high pressure pump.
So are the pumps always located so pull fuel through vs pushing fuel through. 15 ft seams like a long way to pull vs pushing.

This tank is not a water tank. I have 3 of those already. It is just an extra provisioned tank that has been there unused for 37years.

 

[Peter B]

......This tank is not a water tank. I have 3 of those already. It is just an extra provisioned tank that has been there unused for 37years.

Wow, nice boat. I wonder if you have solar panels using all that nice flat and uncluttered cabin top..?

Can't really answer you pump query, as my tanks drain from the bottom, by gravity and just one lift pump on the engine suffices. However, I suspect if there is no lift pump on the engine to use this day tank, then you would need one.

I was just wondering why someone designed a boat that old with a spare and unused tank. Do you have a holding tank as well, or is that meant to be it..?

 

[Mach_cat]

I have a very nice holding tank in the bow for the vacuum flush toilet.
No this is just an extra unused tank. Previous owner had the boat 20. Never figured what to do with the tank. They only made 7 of these hulls some were twins so they would not have the extra tank.

 

[AusCan]

There will be very little restriction or pressure drop over the 15 horizontal feet unless you are using very small hose, or pumping at very high volumes. I don't see any issue regarding the 15 horizontal feet.
The difference in vertical height does make a difference (about 0.3 psi per foot).

Is this extra tank the same height as the other 2?

 

[Mach_cat]

No, the extra tank is below the 2 side tanks and aft of them.

 

[what_barnacles]

If it were me, I would gravity feed to this tank from the other two and use it as a manifold/day tank. Then just plumb it to the existing lift pump.

Test it for leaks first though.

 

[Mach_cat]

Leaks, no problem, when I opened the valve to the tank it vented air at me. It had had built pressure probably from heat. So that should solve the question of leaks.
If I gravity feed, will that be enough to run the fuel through polishing filter?

 

[twistedtree]

Fist, I'd make sure the tank is rated for fuel, and has all the incumbent venting and supply/return ports. Diesel can eat through a lot of stuff.

Personally I wouldn't try to gravity feed through the Racors to the day tank. I'd use a transfer pump.

Check the Racor installation manual about whether to pull fuel through the filter, or push it through with a pump.

As for the other fuel runs, the engine specs should say how much lift it can handle. Compare that to what you have and you will know whether the pump on the engine is enough, or if you need a boost pump of some sort.

 

[AusCan]

Leaks, no problem, when I opened the valve to the tank it vented air at me. It had had built pressure probably from heat. So that should solve the question of leaks.
If I gravity feed, will that be enough to run the fuel through polishing filter?

oooh - That may be a concern. You will need a fuel vent on the tank, unless there is one that is blocked. Otherwise, you'll struggle to both fill it and empty it.

 

[Mach_cat]

As the tank has only one valve in, many things to add.
Inspection port. Inlet valve, vent.
The question still not answered is where do I put a pump.
One from the storage tanks to which side of the polishing filter?
And then going back to the racor from day tank. Would I need another pump.
This tank is fiberglass same as my 2 existing tanks, so what it is made out of should not be an issue.

 

[what_barnacles]

If you gravity feed it, then it will self purge of air (assuming the feed is at the highest point). No need for a vent either just think of it as a sump for the other tanks.

Put in the biggest racor you can afford between the tank and the lift pump. Not so much for flow rate but for filter element life expectancy, and water separation. The bigger the bowl the more water you can deal with before it affects the engine.

If you want to use a transfer pump then tee it after the racor with a ball valve and use the pump to polish the fuel and remove any water build up. Add a timer for the pump and set it and forget it.