We had a concern that our Monten was not gassing as it should, and on reaching out via WhatsApp we received troubleshooting instructions, however when we ordered to replace the cylinders it was found that it was (the cylinder) faulty or not fit for the machine. I’m giving 5 stars because Monten is so quick to deliver refills and looked at the machine & cylinders when they came, replaced the faulty one for free. It’s such an easy machine and service to use, so glad we bought it to enjoy soda water everyday.