Changing oil filter in two line system

JJYork

Greetings! I've changed the fuel oil filter many times on our single line system, and understand the process.

But we had a new boiler installed a few years ago, and it uses a two line set up (feed and return).

Is there anything different with changing the filter in such a set up?

The filter is located about a foot from the burner, at floor level.

The tank is slightly higher to possibly level with the burner (buried outside). The feed and return lines both run across the basement ceiling, 7-8 feet above the floor.

There are valves on both the feed and the return line. Both valves are located about 6 feet above floor level.

Should I close both valves before I change the filter? And then just open both at the same time to bleed at the filter?

Thanks.

Jon_blaney

Pictures of burner and filter would help.

JJYork

I will take a photo this evening. The filter is the typical General red-top canister.

STEVEusaPA

If your tank is above the burner you don't need a two pipe system. If you switch it back to one pipe, don't forget to remove the bypass plug.
But based on your description I imagine 2 pipe was put into service to overcome a vacuum leak somewhere, or someone doesn't know how to properly purge an oil line.
Best would be to find/fix the vacuum leak, then power vacuum bleed the system.
Second best would be an oil deaerator.
Distant third, by a mile, two pipe.

You're not supposed to have a valve on the return line.

JJYork

Here are some photos.

rick in Alaska

Close both valves, change the filter, then open both valves back up before you turn the burner on. If you don't open the return valve before firing it back up, you can blow out the pump shaft seal. If everything is plumbed right, all you will have to do is run the burner and it will self bleed, assuming it can get to that point before the primary control shuts it down. Using the bleeder on the pump will speed it up though.
Rick

JJYork

rick in Alaska said:

Close both valves, change the filter, then open both valves back up before you turn the burner on. If you don't open the return valve before firing it back up, you can blow out the pump shaft seal. If everything is plumbed right, all you will have to do is run the burner and it will self bleed, assuming it can get to that point before the primary control shuts it down. Using the bleeder on the pump will speed it up though.
Rick

Thanks Rick!

Should I also manually bleed at the filter first, like with a single line feed?

rick in Alaska

If anything, put some clean fuel in the canister before closing it up. Otherwise, you should just be able to start it up. I would not try and bleed at the canister as it is not that important, and it can cause more air problems.
Rick

Oilmon

It appears that you have a 1a25a filter installed on your 2-pipe system. Please be aware that that size is too small to properly filter the volume of fuel circulating. A 2a700 would be the correct choice. The 1a25 is only rated for 10gph and will allow too much velocity through the media leading to "channeling". When a 2-pipe system is utilized, the total fuel flow is the pump gearset capacity less the firing rate. Typical residential oil burner pump capacities are approximately 30gph. If your fuel supply is above your burner then you only need a single pipe system. If you need to lift fuel, the best choice would be a de-aerator such as a Tiger Loop. Then the 10gph filter would be more than adequate. 2-pipe return velocities also tend to stir up tank bottom sediments and H20 especially when fuel levels get lower leading to more debris loading of the filter and strainer.