Vertical nipples will freeze up in the winter where I live. I don't see where you are, but if you are worrying about cold weather and don't want to be busting ice out of your setup every cold morning, a system with a bucket heater and horizontal nipples works hands down the best, for me, in USA zone 6. You can use what you will, but sometimes that is not what will work satisfactory for your situation. You don't need to change at all … but you may want to do so. Vertical nipples drip a lot more that horizontal ones, they freeze up much quicker as well. I see they still sell vertical nipples in my area, but only those whom have not been through a winter buy them. Then they will sell you horizontal nipples to get your system to work. They are in the business of selling, that is how profit is made, by selling. There is no guarantee that what they are selling is what you actually want, it is up to you to determine best use practices and implement them. Were you to enquire regarding the various nipples they may tell you, but they may not, or not know. Some folks are just sales people, there to sell.
Below are a few photographs of my setup, a five gallon bucket, a bucket heater, and the preferred nipple in my area. Down south they can use the vertical ones and the like. It is just the cold weather climates that require a setup which works, for best results.
Best to you and your birds,
Edited by RJSorensen - 10/14/15 at 12:18pm