We recently got a Kyoto Yama drip brewer to incorporate cold brew at our shop. We have both the 8-cup and the 25-cup brewers. I've been experimenting with our smaller brewer to get the hang of the process before we actually start selling it.

Does anyone ever have the issue of the grind chamber overflowing? I had the issue at the very start of practicing because I wasn't using a coarse enough grind. Now I'm using the most coarse grind my grinder will allow, and I wasn't having any issues with it until today. After about an hour into the slow drip process, the coffee stopped dripping and the water began to collect in the grind chamber, until it eventually spills over onto the tower and counter. I threw out the grounds and started over, an hour later the same thing happened!

I've been using 100 grams of coarse coffee grounds, and filling the water chamber with ice and cold water. Sometimes I prewet the grinds, sometimes I don't- I haven't noticed any difference in the brewing process from this. I try to keep the drip at 40-60 drips/minute. Usually the brew process will take anywhere from 4 hours, to 8 hours.

Today I did notice the water chamber had a lot of condensation on it, could that be creating extra drips and collecting the water in the grind chamber? If so, why is the chamber still not dripping coffee? It seems it's clogged, though I have done nothing different today from my successful attempts earlier this week. Should I put warm water in the water chamber to prevent condensation through the summer?

Any insight on this subject would be MUCH appreciated! I've tried researching answers and it seems this doesn't come up very often. Am I doing something wrong??

UPDATE: We stuck a toothpick into the grind chamber to release the coffee that was building up inside of it. The water chamber stopped creating condensation so after draining the grinds chamber we resumed the dripping. It seems to be working okay now, no idea on the quality of product we will receive. But we're thinking the extra drips from the condensation created some sort of pressurization in the grinds chamber to prevent the drips.

Does anyone use warm water or room temperature water in their slow drip over the summer to prevent the condensation? Will it have an effect on the product??

Thanks again for your help!!

The flow rate through coffee cake/column will change as ground become saturated. As the coffee fibers swell, essentially it creates smaller passage for the water. Additionally, as time goes by, the fines also clog the bottom filter.

The condensation from the water vessel likely will have minimal effect. The concern could be due to not using coarse enough grind and clogged filter. From my understanding, there is a ceramic filter apparatus in the grind vessel on the Yama. Is it clogged? My cold brew unit uses nylon filter. Some advocate using a paper filter on top of the grind to disperse the water drip, which I don't find necessary. Sometimes if I do that, I have overflow problems and nowadays I don't use the top filter at all.

Aid it possible your grinder produces lots of fine particles when grinding coarse? Maybe sieve then brew and see if it helps? What grinder are you using?

I use a grind between a drip and french press. Never had an issue like that before. Only thing I can think of is the blend or grinder is producing a lot of fines which are plugging our pot up. I built my cold drip brewer and use a siphon pot top with a fine mesh screen.

Stephens Drip-O-Matic 1000 cold brew dripper