Hi all, Posting in behalf of my parents who have just moved into a new house last week, always had a slowly draining toilet but today seemed to get blocked and water slowly draining away. There seems to be an intermittent siphon effect where the water drains lower than the waste pipe is (if that makes sense) and it bubbles and gurgles at times. Cistern fine. Checking outside the waste drains appear clear. All symptoms are intermittent and sometimes it will drain completely fine which is the confusing part to us. Tried plunger and lots of boiling water and then some unblocker all which seemed to help initially. Anyone got any thoughts?? Thanks in advance.