So here is my diy purigen reactor/co2 reactor/ inline heater made out of PVC. It did not come out the exact way I wanted to but it works just fine. On the picture the return is not finish but it just ends with and elbow creating a waterfall into the tank. I will also be addind ball valves before and after the filter housing so that I can change the cartidge( did not think about that at first....). The whole thing sits just behind the tank and is hooked up to a pressurized co2 system.
@Chronados: No I do not use one of those, it is simply siliconned on the outside and I pourred PVC cement in the inner part to make sure it is water tight. No leak but taking it out will not be fun. And just so you know, The filter housing is only for polishing water and making a purigen reactor as I am using a Rex Griggs too(on the right handside) for co2.