There are no manufacturers who authorize sale of their product over the internet. This will seem odd, since a quick internet search will find you plenty of online distributors who are selling every brand under the sun (including some BIG name companies). Don’t let this fool you. If you are contemplating purchasing your tankless system online, call the manufacturer of that product and ask for written verification that your internet purchased product will have a valid warranty. You’ll find out quickly that internet sales are not authorized.