Isomac Tea pump check

#1: Post by **jjmiller52** » January 10th, 2022, 6:46 pm

Hi all, I have a Isomac Tea, version 1. How many ml/oz. should you get in 1 minute with no portafilter? I get 16 oz. in a minutes time. Having just replaced the vibrating pump, does that seem about right? If not, what should I look into? Thanks

#2: Post by HB » January 10th, 2022, 6:56 pm

More than likely you have a Ulka E5 pump. If so, this graph from another thread shows the flow rate at a given pressure:

HB wrote:Check out this diagram from Espresso brew pressure - conflicting answers:

For vibratory pumps, actual brew pressure is inversely proportional to flow rate. The higher numbers you hear quoted for vibratory pumps refers to their maximum pressure at zero flow. At double espresso flow rates, most are around 9 to 10 bar. The OPV adjustments you read about only apply to ristretto flow rates. If you want to experiment with low brew pressure, say 7 bar, then an OPV is a must-have. But if it's in the typical 9-10 bar range for double espressos, the OPV does nothing.

So at 0 resistance, the flow rate is ~650 mi/minute or 22 ounces. Since your pump is pushing water through a gicleur at the top of the grouphead, your reported 16 ounces/minute seems reasonable.

PS: For those following this thread, the OP asked a related question in Low brewing pressure.

January 11th, 2022, 12:17 am

Thanks for the reply. As for as that graph goes, it's Greek to me. If you say my 16oz per minute is reasonable, that's good enough for me. Thanks again.