Found my answer here in the Grundfos guide, diagram 3. So it's check valves and balancing valves on both of the return legs before the Tee.
My sister's 7 year old house was plumbed w/ PEX and came with on-demand hot water -- but instead of spending the extra $30 worth of PEX to run a return loop, the builder used a crossover valve (which has failed). There's easy access to the lines in the attic, and we want to run a dedicated return -- no big deal --- except the place where she really wants the hot water on demand is at her kitchen sink, and it's at the end of about a 25' branch.
The kitchen sink is in an island (on a slab), so I can't run a loop to it - but there is an unneeded 3rd line from the island to the wall (to tie the ice-maker supply into an undersink filter system). I can use this as a return as denoted with the dashed lines, but I've got a feeling that if I just "T" it into the main return, it's either going to short-circuit the return for the far bathrooms, or be bypassed.
Am I right in thinking that a simple Tee won't work? If so, any suggestions? Maybe a passive crossover valve at the kitchen sink (from the hot supply to the return leg)? Check valves? Both?
Last edited by jeffeverde; 01-08-2011 at 07:40 PM.
Why not just replace the "bypass manifold" valve and add another at the sink? With the system that was installed, you can install the bypass valves ANYWHERE you need one.
Because after getting scalded in the shower with full hot being delivered on both sides of the valve, no more crossover valves! And with easy access to run a return line, and already having a recirc pump with timer, why not do it right and put in the dedicated return?
The crossover valve was NEVER intended to be a "forever" unit. Usually they have to be replaced every few years, and there are symptoms long before it gets to the "scalding hot" cold water lines that its time has come.