Phil L wrote:
The Natural Philosopher wrote:

yes. The only downside is pongs. If these are floating up from
gulleys or plugholes, then consider trapping those individually. Or
source a rubber plug from somewhere that fits. Or modify what you
have to take a standard rodding point.

Forgot about those.
To the OP, you can buy a rubber bung with a butterfly screw which
tightens and seals the hole, they are made specifically for drains
and you can get one from any builders merchant, or maybe even b&q.

Look for drain test plug on google, a 100mm (4 in) one will set you
back about 8 - 10 quid

typo fixed, 100mm not 200mm

--
Phil L
RSRL Tipster Of The Year 2008