Originally Posted by Pete7
The other thing you could do is measure it with a tape measure then use google to calculate the volume which would confirm if it really is a 180L tank.
What's the tank made from? if it is stainless steel it should have baffles for that size which means looking inside is difficult. What you might see however is the pick up going to within 1/4" of the bottom of the tank. However what the fabricator did on the day he made it...........
Nothing lost having a good look, would also show any water / dirt etc inside.
L x W x H (in cm) = volume. Divide by 1000 for capacity in litres (ignoring material thickness). Divide again by 4.54 for imperial gallons.