David filter. Where does the small o ring go?

[pcatterall]

Embarrassing to ask as I am having a big senior moment.
I am fitting a new cav filter unit on my polisher and have forgotten where the o rings fit!
I'm clear about the two large rings and the very small one but can't suss out the one which is around 10 mm diameter. Pat Manley's book only shows the two large ones. I will reexamine the unit and follow the way that fuel flows to see if I can determine the position by logic! But meanwhile why not ask my expert chums?
Will also try on line but it is probably full of amateurs videos rather than diagrams and text which is all my brain can handle!

 

[Spyro]

If it's the kind I'm thinking about it fits around the long bolt under the top plate if you can look under there you should see it.

 

[PaulRainbow]

One small one fit the spigot that goes into the top of the filter and the other fits the bolt.

 

[pcatterall]

Thanks, spotted!
Had a look up there with my mirror. I guess it prevents unfiltered stuff from mixing with what has passed through filter. Need the mirror to ensure it is seated. Quite a bit of force needed to push filter over it to seat properly with top seal but all working well now. No drips or air seen. Just trying to polish a full 50 gallon tank, 4hours calculated!!
Cant Edit title........predictive text again

 

[pvb]

... but can't suss out the one which is around 10 mm diameter.

It goes in a groove on the underside of the filter head, onto which the filter fits. You can see the groove on this image...

 

[pcatterall]

Thanks pvb, good picture!!

 

[PCUK]

It's the same on my Reginald filter!