[Joe Galowitch]

Hello Guros I have another question d0es any know why there’s a big blue tank attached to the 12volt compressor?

[Richard]

Are you sure it's attached to the 12V compressor. Big blue tank in that compartment could be the air bladder/water storage tank.

[Joe Galowitch]

Are you sure it's attached to the 12V compressor. Big blue tank in that compartment could be the air bladder/water storage tank.

Well that’s what it looks like but there are no hoses attached. I took a couple of pics will see if I can get them posed. Also there is a schrader valve on top.

[rheavn]

Sounds like maybe a water pressure tank, but that's just a guess.  A picture or two would be very helpful.

[Richard]

Look at the very bottom for a piping connection, there will only be ONE connection.

[Joe Galowitch]

That’s it 1 fitting soi guess it is for water.

[Richard]

looks like this
   

If you find the water pump is cycling on and off rapidly, then the bladder in the tank has leaked down. With the water pump off, and a faucet open, use the air fitting on top to check the bladder pressure. I have found with my system that 25 to 30 psi works great.