OK so here's a summary of how to make once you have all the parts:
First cut the acrylic tube to length. I cut to 350mm but you could get away with less.
Now prepare for bonding into the PVC socket and elbow. I took the corner off the cut tube with a file and roughened the length that will engage into the socket a little using coarse sand paper.
As mentioned previously the thin polyweld is very thin and drys fast so suggest using medium. I coated both surfaces with plenty then inserted tube until fully engaged. I brushed a little more at the join where the tube goes into the socket and it was pulled into joint. As the tube is clear you can see if you have a good bond. Repeat this for other end.
This sealed fine for me as it ran for a few days. However I had a small leak where the hose tail screwed into the reducer bush. As fixing this required removing reactor again and sealing threads with silicon I took the opportunity to run a bead of silicon around the tube just as a belt and braces to the polyweld bond.
Next prepare the reducer bush to accept the CO2 intake and the valve for venturi or bleed. For this you need to drill two holes in the bush.
You're wanting to drill the holes in the "sweet spot" ensuring that you don't break through the outer threads nor the inner.
In the first photo you can see small indents in the moulding around the outer edge of the top face. You want to drill directly between a pair of these and roughly in the centre of the material. If you're central to these indents then the tubes should have an intact web supporting them on either side as in second photo.
I drilled a pilot hole of 3mm first- drill at a slight angle so that you avoid breaking through the external threads. Then open the hole so it's a nice snug fit around the 7mm tube; I can't honestly recall if this was 7mm or 7.5mm.
To prepare the white PVC tube cut one length so that's it extends almost to the bottom of the clear reactor tube (see photo in original post). Cut the second one about 50-60mm long so it only extends slightly into the reactor.
You'll notice in one of the photos above I show a check valve in the CO2 intake line. Nice idea but it desolved and snapped off when I applied polyweld to whatever plastic it was made from! Therefore I just used a straight 4mm airline connector. You can also see I have cut the mounting pad off the blue algarde inline valve.
To fit the blue connector and inline valve into the white tube you need to use a drill to open the ID slightly until they are a tight fit. I used the polyweld to bond the fittings into the white pipe. Once set for extra security I applied some araldite. I then used polyweld to bond the tubes into the prepared holes in the reducer bush. Again for extra strength I applied araldite around both top and underside where the tube passes through the webs. When applying to top don't put too much so that the hose tail won't seat.
Once set trial fit the bush with white tubes into the reactor. The bottom end of the long CO2 inlet tube will probably be contacting the inside of the clear reactor tube because the hole was drilled at a slight angle to avoid threads. This is easily resolved by softening the upper part of the tube in the steam from a kettle and bending so the injected bubble will be roughly central.
I originally only used PTFE tape on threads but as mentioned I had a small leak. I'd therefore suggest using silicon on the threads when screwing together. Don't over tighten; especially the hose tails as the wall is quite thin and they'll easily snap.
All you need to do now is add the venturi loop and hose configuration to suit your set-up. To install the 16mm ID Ehiem hose onto the 22mm tee and 20mm hose tails soften in either the steam of the kettle or dunk the end in a boiling kettle.
Hopefully that's of assistance.
B4M