testing diy mash tun

Morning,

I recently made a mash tun from a cool box and copper pipe manifold. This went out to a plastic tap. I tested this with water. It kept temperature fine and emptied fine. I decided to make a beer this weekend. Everything was running smoothly, I ran some wort out and put it back through to settle grain bed etc then began to sparge. It quickly blocked and became impossible to drain. I had to move the graiin to a grain bag and try sparging that way. I ended up at around 40% efficiency and what might end up being a cloudy 2%abv ale off the back of it. I have now fitted a tank connector and a ball valve which should sort this horrible problem but I am a little scared to brew this weekend without testing it.

My question is what could I use in the tun to test to mimick graiin? I want to see if new tap will block up etc. Porridge is cheap but too stodgy. In retrospect I should have kept the spent graiin but it is now long gone. Thanks in advance for any advice.

Ben

 

Maybe try using rice.?

 

I was thinking maybe rice and porridge oats to try and get something similar. Just don't want to waste grain or end up with a poor quality beer.