DIY Immersion Chiller Copper - 3/16 OD?

[Shinjuku]

Hi all. Looking to make an immersion chiller on a (extreme) budget. I've been doing research and reading articles on immersion chillers. Most say that a longer length thinner coil will work better than a thicker shorter coil. E.g. 15m at 8mm will chill quicker than a 10m at 10mm. I've been looking at coils and found this item > HERE. My plan is to make the chiller as small as possible so it can be more immersible, or even join 2 together since the price is lower compared to 1x25m coil at 8mm (£25)

Wondering if anyone has made or used an immersion chiller below 8mm in diameter as this seems to be the norm?

 

[RoomWithABrew]

"It's more than just length and diameter" as the actress said to the bishop.

Rate of flow through the coil and the temperature of the water you put in also will factor greatly into how well something chills your wort.
If you put your chiller in to the kettle and don't stir continuously or move the coil around it will take longer to chill as well.
If the water is coming out of the chiller at wort temperature then the flow might not be high enough so consider that as a factor.

15m of that pipe and a connector to join the lengths together and connectors to attach pipes to each end will probably cost more than 25 pounds anyway, there'll be a fair resistance to flow with that narrow pipe.

I was able to warm the hosepipe up and just force it over the end of my immersion chiller that came with the robobrew so no new connectors. It was 10mm and worked fine.
If you are on a water meter do factor that in to your calculations and also consider making a counterflow chiller if your system has a pump.

Sometimes a little bit more works out less.

25metres of 8mm copper coil seems very cheap and would have a bigger surface area for cooling than the 3/16 at the same length.
In fact 0.628 square metres for 8mm in comparison to 25 m of 3/16 which is 0.37 square metres and you'd need 4 lengths at 11 pounds each with 3 connectors to get that length. BTW 7.62m x 4 still only has an area of 0.45 square metres factoring in that about 40cm wont be in the wort.

 

[Buffers brewery]

As @RoomWithABrew says the mains water temperature does have an impact on how quickly you can chill down but also how low you can go. Here in the south the mains water can get quite “warm” in the summer which significantly slows the process. The way I fixed that was to have 2 chillers, one in the wort the other in a bucket of ice water and connect the chillers in series so the mains water is chilled before it goes to the wort chiller (I know you’re on a budget ). I use 10m x 10mm copper tube.