Hi,
I have a magna clean filter (black top, red bottom) which was installed before I moved in to the property. I cannot for some reason remove the cap that is only suppose to be hand tight. I have used the key, tried it when it was warm, jiggled it a bit, bled the valve but no go. I have used force but don’t want to damage the pipes. Any other ideas? Clearly this thing has not been serviced for a long time!