You have probably got this but:
After a year any petrol still in the system probably wont be petrol any more , so it will be best to drain it.
Getting a sample out to prove this would be a good idea.
If it smells like varnish its has gone bad. It should sting your nose when you smell it - you can tell the difference.
The tanks could be emptied by loosening the balance pipe joining the two tanks ?
Whats in the rest of the system will probably need flushing somehow - use the pump to flush it out ? ( highly dangerous of course !!)
