All I can say about gate valves is you will get what you pay for, in terms of quality, and how long it will be before they start leaking. The valve stem especially. The higher priced sch 80 valves, are going to be better, and with Viton seals--will not leak as soon, as those with EPDM seals; and the better valves can be taken apart and the seals replaced, rather than having a disposable valve. Hunting up a good price on a quality valve is a better deal, and aquarium suppliers don't always have the best price, though sometimes they do.