If you have small enough orifaces in the header water line fittings you should not need the t valve. The t valve shuts "all" water off at idle to the headers. However if you have too much water then the t valve is one way to control it. Any raw water exiting the pipes is too much and is typically what causes water in the oil. You should just have steam and it should be barely visible at WOT. You also need to keep your "weep holes" in the bottom bend of each primary tube open. They are there to drain any small amount of excess water that might otherwise accumulate and get in through the exh valve from reversion. If you need any help just give Bob or Tom a call in the AM or email your phone to sales@rexmar.com and they'll call you. There are many ways to control header water too extensive to type out here.