The west country club have conceded just three tries during an unbeaten start to a campaign which began with many pundits tipping them for relegation.
Victories at Worcester and London Irish sandwiched a draw with Saracens which has set up tomorrow's Memorial Stadium showdown against league leaders Wasps.
Wasps' impressive early-season form of three straight wins represents a feat they have never previously achieved in Premiership history.
And Hill knows it could be a long afternoon if Bristol fail to maintain their defensive excellence against such potent attacking threats as Wasps trio Tom Voyce, Paul Sackey and Josh Lewsey.
"We watched their game against Harlequins last Sunday, and they ran riot," said Hill, recalling Wasps' 42-23 triumph. "They should have scored eight tries.
"It is going to test our defence, but our defence has been very good so far - the best in the league - and it is going to have to be right at its best to hold Wasps.
"It is relatively simple. Wasps keep coming at you, wave after wave, and if you are not back on your feet quickly after the tackle, then holes appear and you are in trouble.
"Wasps keep the ball for multiple phases, and it is going to demand a huge defensive effort from us.
"If we are to get anything out of this game, it will have to be one of those days when everyone defends to the best of their ability. It will be a hard old game, but we hope to do well."
Bristol will be without flanker Joe El Abd (ankle) and centre Rob Higgitt (nose) after they were injured during the Irish clash, so Hill has called up Alfie To'oala and Josh Taumalolo as their respective replacements.
A back division reshuffle sees wing Craig Morgan switching to full-back and David Lemi starting in the number 11 shirt, while prop Alex Clarke features instead of Dave Hilton.
Hill said: "Alex has had limited opportunities, but he has impressed us and deserves his start.
"He was troubled by a shoulder injury last year and he was never quite right, but he has had that sorted out and he is like a different player now."