 When the lower chamber is almost empty, bubbles of steam mix with the upstreaming water, producing a characteristic gurgling noise.This "strombolian phase" allows a mixture of steam and water to pass through the coffee, which leads to undesirable results, and therefore brewing should be stopped by removing the pot from the stove as soon as this stage is reached.Moka pots require periodic replacement of the rubber seal and the filters, and a check that the safety release valve is not blocked.