if you remove your chanter body so that the brass cap is still attached, block the cap with your hand, pump the bag up and find that airtightness up to the cap is intact - but you then lose air when the chanter body is attached - what’s the next step in trying to diagnose the problem?
If you want to test if the air is leaking out of the space between the chanter and the chanter top, make a temporary “gasket” around the base of the chanter top using blu tac (poster putty).
Reed seat.
Keys.
Fingers. I’m betting on fingers.
How ‘intact’ is your initial Bag airtightness ? I suggest; firstly to inflate your bag fully with the exit blocked, then sit on it with all your weight… you want it to stay full with no deflation.
Then check your chanter by removing the reed, cover the holes in the normal way, use a good popping strap, not your jeans, to block the bottom and then blow by mouth into the chanter. Use all your blowing strength, make your ears pop… yes it is uncomfortable, sorry. This should check that your fingering is correct and that no keyed holes are leaking.
Do check; any keys for tightness in their movement, any springs for weakness, any pads for poor condition.
Check also the binding that seals the chanter to the chanter head and check the chanter head bore for Ovality. With a wooden head Ovality can happen due to shrinkage of the wood (in server cases the wooden head will be smaller in diameter at the exit than further back down its bore… this makes for a very wobbly joint that is difficult to seal)… with a Brass tube chanter head some Ovality or miss-shappeness can occur due to an impact.
I decided to try this , I’m now on the way to the vet to have the wooden plug that shot out of the chanter stock removed from my dogs rectum. It maybe OK for Geoff to do the test but what if you weigh 25 stone ?
RORY
Hello john,
it also could be the stop-key gasket or any other key if not the fingers, skightly lifted - happens sometimes
Oh! I really feel sorry for your dog.. still a visit to the Vet was a welcome relief I’m sure, for the dog, from all that Piping .
If you weigh 25 stone then perhaps it is best to put only one cheek on the Bag during this test 
Yea cheers Geoff, the dogs fine but it took some explaining to the vet, anyway he got the wooden plug out but I have to admit I’d never seen a corkscrew used in that way before.
RORY
On a more serious note; as a person whose weight has fluctuated between 10 and 15 Stone (140 - 210 pounds or 63- 95 kilos) during the years that I have been a Piper I can confidently suggest that it is much more comfortable to play the pipes when one’s stomach is not getting in the way.