5m, that's what, a bit over 15 feet? It will take a while to chill a 5 gallon batch. A longer coil would be much better. I would at least double that. 50 feet is good. You get plenty of heat transfer, and use less water. For such a short coil you would probably want a second coil immersed in an ice water bath to cool the hot cooling water, and a pump to cycle it. No savings there! Except maybe saving water.
My own opinion is that a chiller is worth it uniess you are going the Australian no-chill method. An HDPE "cube" jug, 5 gallon size. Fill it all the way to the top with hot wort. squeeze so there is no air in it at all, cap it, and forget it for 24 hours. Many brewers would recommend an extended boil time to get rid of DMS precursors. Some say don't bother. Anyway this keep the air off your wort while it is vulnerable. Make your starter when you transfer to the no-chill cube so it is good and vigorous when you are ready to transfer wort to fermenter and pitch yeast. That way nothing much can compete with those billions of yeasty cells.
Bad batches happen. But when you make a good effort at doing everything according to accepted best practices, they are rare. If you just go for it, and don't sweat the small stuff very much, bad batches are still rare but will happen more often than when you keep everything as close to perfect as practical. Of COURSE you can brew without a chiller. And I don't mean the "no-chill" method of chilling in a jug with the air squeezed out, either. I mean just leaving it in the kettle until cool enough to put in the fermenter, and leaving it there until cool enough to pitch yeast. It has been done a million times. Doing it that way or not doing it that way is your decision. You know the costs, and you know the risks. Your beer.
My batches to date have been mostly with an immersion coil, 50 foot, copper. My very first batches were kits and I used the ice water bath method, then I bought the coil. It cost about the same as buying 50' of copper tubing and it was already formed. One time I forgot to put the coil in the wort while it was still boiling and I went to the store and bought a couple blocks of dry ice and dumped in. Buy that was fun. Probably no need since it was still hot enough to sanitize the coil, I think, and anyway I was a half hour going to the nearest store and back that had dry ice. But it was really cool when the neighbors saw the thick fog rising from my bubbling cauldron! My next batch will be no-chill and I have high expectations for it.
A good HDPE jug that is food safe and is safe to pour hot wort into, is probably going to be a lot cheaper and less trouble than a coil, so if you must save money, that might be the way forward. Not doing anything but letting it cool overnight can work but will increase your slim chances of infection. I consider it the way back as opposed to the way forward. A nice vigorous one quart (one liter to you!) starter of the same gravity as your wort more or less, will help reduce your chances of a bad infection, should you decide to go old school. But I wouldn't even bother with a 15 foot coil. It will take forever and use up a lot of water.
. I can buy a 5m (approx 17ft) roll together with the correct connectors for ā¬30 from my local DIY store coil it round a pot of the correct diameter and the job is done.
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