In message .com,
popgun writes
Dear all,

I've had a quick search through the group and have found some earlier
threads which touch on my problem, but I thought I'd run it by the
group as I'm still perplexed.

Does anyone have any suggestions or advice? I'd really like to have a
few ideas before I call in a plumber.

Pongs from drains snipped...

Are you in the habit of tipping buckets or saucepans of water through
the grid?

I discovered that the plastic gulley outside my sister's kitchen is
fitted with a removable bung allowing access for rodding. A sharp inrush
of waste is sufficient to release the bung allowing the sewer pipe to
vent to the air.

regards

--
Tim Lamb