Cleaning Fiberglass Barrel Reservoir?

[Highatollah]

So I have a standard FDA blue fiberglass 55 gallon barrel that I have used for my reservoir. It was sitting for awhile but it is time to use it again. However the top is not removable so I can't reach in and scrub it.

My question is will filling it with bleach water be enough to disinfect it without being able to scrub the walls inside?

That's all, thanks.

 

[DemonTrich]

I would use a 25/75 bleach to tap water. Then using a power washer like at a car wash, hammer down and spray really good.

Then rinse at home with a garden hose super good.