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DIY Project DIY Reactor - pictures, assembly and testing

Ed Seeley

3 Jul 2007
I decided to start a new thread for this so it doesn't get cluttered up with the other one.

First of all let me start with the plan so you can see the development of it. This is the line-drawing of the reactor design.

It has a half metre length of clear PVC, Grey PVC socket and bend at either end (they don't do the clear fittings in metric measurements!), 2 threaded reducers (to bring the 1.5" threaded sockets to 1/2" threaded) and 16mm or 12mm hosetails that fit into the 1/2" reducers.

The CO2 is injected inline ahead of the reactor (using a reducing tee) so the CO2 and water are already mxing up before they even enter the reactor. The water/CO2 mix enters at the top of the reactor and then rushes and swirls around in the large reacting chamber. By the time the water reaches the bottom of the reactor there should be no bubbles left at all in the water so bubble-free, CO2 enriched water will be reutrned to the aquarium.
The clear pipe arrived in 1, 5m piece!


After the 50cm length has been cut all the pieces are assembled,

From rear left the parts are;
2, 50mm pipe clips,
Below that a 50mm to 1.5" threaded bend,
50cm Clear PVC pipe,
Next to the pipe, 50mm to 1.5" threaded socket,
Next to that the pipe cement,
Below those the 2, 1.5" to 0.5" threaded reducers,
Below those 16mm to 0.5" barbed hosetails (which are the right size for 12mm aquarium hose, not 16mm)
Finally, next to them, 1 4mm airline valve.

(I have detailed close ups of these pieces but didn't think they added to the post! They are all here in my album though if you want a look.)
The hosetails screw into the threaded reducers, which, in turn screw into the straight connector or the bend.


To fit the bleed valve I needed to drill a hole. Obviously this hole needs to be close to the top of the rector as possible. I had originally planned to put the bleed valve at the top by drilling through the threaded connector so the valve was pointing upwards. However this would have really got in the way with the hosetail and could have meant there would be problems fitting the hose onto them so I've fit it at the side.

To do this I had to drill a 5mm hole all the way through both the side of the straight connector and the threaded reducer. To do this I simply screwed them together tightly and drilled stright through both. I then removed the fittings and checker there were no problems - which there weren't! For the other that are going to be siliconed sealed in the thread I will assemble them and drill afterwards.


The bend and straight connector have been glued into the pipe,


It's now drying as it needs 4 hours to fully sure before use.
Here's a picture of the assembled reactor.


Total length is 65cm so it's a bit of a beast! Once I start testing later we shall see if 50cms of pipe is really needed as I'll be able to see the bubbles mxing around. I'll also try out the different options of filling in the reactor but I'll run mine empty. I'll try bioballs and a mesh netting material to see the difference. It might also prove whether these are any help or not with diffusion.

You guys getting one better measure your cabinets/locations again to make sure it'll fit!
LondonDragon said:
Looking great Ed :) can't wait to see it in action :)

Cheers Paulo, I'm itching to try it too, even though it'll be with the smaller pipe so I won't get full flow!
Ed Seeley said:
Cheers Paulo, I'm itching to try it too, even though it'll be with the smaller pipe so I won't get full flow!
The full assembly looks great mate, most impressive, great DIY skills :) Been tidying up my cabinet so just going to measure it again to make sure it will fit, but I don't see a problem with 65cm. I might try it on my Eihem 2224 just to see if it reduces flow or not.

Great work :)
aaronnorth said:
looks very good, so which direction is water flow? Into the curved end or from it?
If not mistaken water should go in through the curved bit, with flow against the raising bubbles of CO2.
LondonDragon said:
If not mistaken water should go in through the curved bit, with flow against the raising bubbles of CO2.

No water will enter where the straight connector is. Thats why the bleed vavle is there, so you can bleed the air out.

Looking great Ed. If you get enough interest for a second batch i will sure be interested.

Just a thought could this be used at an angle if it wont fit upright in the cabient as it is?

Cheers Gordon.
Yeah the water goes in the top so the water is pushing the CO2 down and mixing together.

Cheers for all the compliments guys. I've done way more than my fair share of pipework having built a few ponds! It certainly makes it easier when you've the confidence of having done it before as you've only got a few seconds before the joints stick together!

Well just done the first test and silicone sealing the threads is definitely the right choice! There were a fair few drips of water from the joints! Actually the worst bits were where I'd used some 12/16mm pipe to build up the connectors - water dribbled out of there!!! Once the new 20mm hosetails are fitted that will solve that!

However there was time to give it a quick test (with a bowl underneath to catch the drips :lol: ) and the effect was great. I opened the bleed valve and it rapidly removed almost all of the air. Once started up the air that was left was removed by the water flow in about 5 minutes. I didn't get chance to fit the CO2 line in but will do that tomorrow and take some pics. I'm going to reseal the threads with more PTFE tape tonight so it doesn't leak too and try and seal the other fittings up a bit better so I can run it for a couple of hours tomorrow. Will take some pictures of it running too and try some media in there (though I'm now sure it doesn't need it).
Ohhh, I'm getting excited about this now :) Mine's not going in my cabinet so 65cm should be fine. (Though have made a quick measurement and while 65cm would fit in my cabinet there wouldn't be enough room to get a gentle curve into the top of the reactor!)
Well big cheers for PTFE tape!!! :lol: Everything sealed now, except the temporary fitting I am using to inject CO2!

I haven't yet tried it with anything in there as it's working so well with nothing!

Here's some pics;
Reactor in position.

Top showing air/CO2 bubbles swirling around,

Micro bubbles of air near the bottom,
LondonDragon said:
Looking good Ed, do you notice any escaping into the tank?

Some air bubbles yes as there's a small amount left after bleeding the reactor. But once that was mixed in there was nothing!
That's looking good, but my what a beast, i reckon that will be too big for most of the cabinets around.

Good work though i must say.

Cheers Gordon.
Cheers guys.

I don't think it needs to be that big at all after running it. I reckon 40cm pipe for high bubble rates and 30cm would do for standard ones. But too long can't hurt as you can then really ramp the bubble rate up if you need to! I reckon I could run a constant stream of CO2 into it with only a few bubbles coming out!

That's no fish room!!! Those are two of the tanks in one bedroom! I will take some photos half term after I've had time to tidy them and the corner where they are up!!!!
Just been experimenting again.

I have the BPS at about 2bps which was a little less than I needed to get 30ppm on this tank with a diffuser (IME reactors are much more efficient so I'm keeping a very close eye on the fish).

There are a couple of micro bubbles coming out of the filter outlet into the tank every few seconds at 3bps or so and, when I turned it up to a constant stream there were quite a few, almost like they were coming from a ceramic diffuser! However this bubble rate would quickly OD the fish I'm sure.

I'm going to have to turn it off again in a bit as the old brass valve I'm temporarily injecting the CO2 through is leaking where it joins the plastic! The rest of the reactor is now totally waterproof.

The next experiments will probably be this week once I've glued a plastic fitting into the pipe for the CO2!!!
Ed Seeley said:
The next experiments will probably be this week once I've glued a plastic fitting into the pipe for the CO2!!!

I thought you had sourced a T piece for this Ed?

Or are you still waiting for those?

Cheers Gordon.