Often times the hose/line will simply pull far enough out of the way to get the wrench on or possibly, the canister can move by pulling gently on it away from the wall so the fastening bracket movement allows for the wrench to slip on.
You likely could relocate the canister/housing a little higher too. Photos would help us visualize.
You'll need a little room under the canister for removal anyway.
Don't forget to turn the water supply off and relieve the pressure before trying to remove the canister.
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