A simple, but effective, Clock Face Contents Gauge.
This can be used with many types of liquids and is for measuring the contents level. It is manufactured from a strong plastic and this gauge should last you for years with proper use. The clock face displays the level of the liquid in the tank from 'Empty' '1/4' '1/2' '3/4' through to 'Full'
It is very accurate and it can be retro fitted to your tank (both plastic & metal) by using the 1.5 BSP thread connection. You should have a spare 1.5' connection on a metal tank and some plastic tanks but you can always drill another hole in the tank to suit this gauge if there isn't a hole available.
There are several different float lengths available to choose from to suit your tank size: Simply measure the overall height of your primary tank and select the correct height float gauge for your tank from the drop down height selection button.
Further to this, it is also possible to fine adjust the float gauge string for more accurate measuring of the tank contents