I am attempting to build a photobioreactor, in other words a water-filled system for growing algae. I'm using a series of 1.5" clear tubes to hold the water, the bottoms of which will connect to a PVC manifold I've assembled by gluing a bunch of tees together. The nominal pipe/fitting size I'm using is 1-1/4" schedule 40 PVC.
There are ten tubes (currently) and I need to be able to bubble air through each tube to deliver carbon dioxide to the algae. I don't know how to run the air tubing into the manifold underneath each tee to deliver the air bubbles. The tubing and fittings I'm using for air are actually 1/4" drip irrigation parts.
I'm attaching some photos of what I have tried so far:
First attempt: drilled 1/4" holes, pushed tubing in, silicone around each hole. Result: leaks
Second attempt: Enlarged holes slightly (5/16"), siliconed the "misting" drip irrigation fitting right to the hole. Result: came apart during handling.
My next attempt was going to involve enlarging the hole and tapping 1/4" NPT threads into the wall of the fitting, and screwing a barbed adapter directly in. The reason I didn't do this from the beginning is because of the cumulative cost of all the extra fittings. I'm looking for other suggestions or perhaps some part or fitting I've not heard of that will make this easier.