I have a gravity system. For the HLT, hot water, I have a ten gallon pot with a valve, sight tube and a turkey fryer burner. That drains into my mash tun which is a round 10 gallon Rubbermaid cooler with the braid from a water heater supply line for the filter. That drains into my boil kettle. A ten gallon SS pot with valve on an SP10 burner.
I do batch sparging and this rig works well.
edit there is nothing changed in the lid of my cooler.