Fuel Filter Air Leak

http://www.ebay.com.au/itm/Mercedes-Benz-CDI-diesel-fuel-line-o-ring-seal-601-997-06-45-6019970645-x-6pc-/181407375404 cost about AU$21

The filter I had bought (the second one in fact) was one without the Water in Fuel sensor on the bottom and the water purge screw on the side.
I replaced the fuel lines and there was air leaking into the system.

I now know my van almost certainly has no pump in the fuel tank so relies on a pump on the motor to create a negative pressure to draw fuel up. This means if there is any leaks it will draw air into the line.
I feel this is most likely coming in at the O ring on the outlet central non return valve connection. On the sprinter forum people report problems with ingress of air at the Water in Fuel sensor and the return fuel line as well as mostly at the out-take. Some people eliminate the possible leaks by putting in a filter without water sensors and even without a fuel return, taking the fuel straight back to the tank.
I purchased a new correct filter in Canberra on the way to the snow and also a hand priming pump and 10mm plastic hose to be able to prime the fuel filter easily.

Here is a link to a Jeep site about installing a Facet Fuel pump before the fuel filter and wired to the glow plug circuit to prime the fuel filter

Here is a link to the O rings that go in the fuel line from the fuel filter:
Part Number is: A 601 997 06 45 (which should be a pack of 6) or 601 997 03 45
Here is the pump he used

Here is another idea to use a pre filter… not so keen about that but maybe
and here also

This thread mostly talks about using the filter without the water in fuel sensor and purge valve to reduce the change of them causing the ingress of air.

These are the hose clamps to use but need to get the OD as I only know the ID

HERE is a link to Sydney Filters which sells the genuine MANN filter for about $52

ordered O rings from Moldova for US$14 on 2nd August 2016 HERE