I purchased an Eco Smart 18 in 2016 and the reason I purchased this brand is because it came with a lifetime warranty. Here it is three years later and one heating element is burnt, the cylinder it sits in is leaking and I have no hot water.
I also have a smaller ECO in a duplex that has been replaced no less than three times. All were purchased from Home Depot and they were nice eneough to exchange the smaller versions fo me three times. However when I asked about the ECO 18 the person's in the plunbing section at two different Home Depot's said they no longer have ECO hot water heaters in the stores because of constant returns and problems.
I called ECO and their response was they are not going to warranty it because the warranty is "Inactive" whatever that means, the product was registered online in 2016 by me so there is no excuse. My advise to anyone looking for a hot water heater is to steer clear of all ECO products (made in China) and look elswhere. Just dont do it if you want piece of mind!