A well designed system has a vent, my honey dipper told me on his
annual visit about 3 years that part of the problem was that mine was
installed with no vent, and it has to have air to ferment. I put it
back together with a stack and made a flowerbed around it, haven't
seen him since, I miss him, but don't miss the back ups and expense.
Likely the tubes are vents and clean-outs, no rocket science here, make
them as tall as you like, use standard PVC tubing and couplers and
glue. He may curse you if you make the clean-out too tall, but it can
always be trimmed later. I used a 20 galon PVC drum I got from a
car-wash service guy and cut to to fit & made a removable lid from the
bottom of the drum. this made so the clean-out lid could just lift
through the opening and nothing seals well enough to exclude air.