Just finished installing a Rinnai V65i, and it seems to work great...... in the kitchen sink. and the bathroom sink. But when we turn the bathroom tub on it seems to "rev up" then slows down. Water gets hot for about a minite, then the heater beeps and throws a code "12". All lines are the same size and flow rate, but the bath tub makes it wig out! We have tryed running both sinks at once just in case it was an excessive flow problem. Both sink work well when used simultaniously. We have used the "approved" Rinnai hot and cold inlet/ outlet valves with Hot pop off. And the weird Rinnai double wall venting system. This is a brand new install replacing a std 30 gal. propane tank. Any input would be appreciated.