Customer stated tankless water heater was getting error code 10 and no hot water. When turning water off and back on unit starts working again. Contacted customer support and Andrew recommend verifying venting is not blocked. Cleaning out burner chamber and also replacing exhaust fan inside tankless water heater. Due to water heater being 12 years old and no warranty or guarantees on repairs CPI plumbing highly recommends getting water heater replaced. Provided estimate to perform repairs recommended by customer support. Also provided estimate to replace tankless water heater. Customer is going to look over options. Will have to adjust pricing for installation due to venting issues. Informed customer about venting issues. Thank you for choosing CPI plumbing and Heating