Pressure balance tub/showers & insta hot/on-demand systems don't work together well??

[I love pizza]

I'm curious what you folks have heard good and bad about pressure balanced tub/showers and insta hot/on demand hot water systems. I've heard stories lately that some insta hot or on demand systems make the hot pressure a little lower than it normally is and because of that any make of a tub/shower that has a pressure balancing spool will cause that spool to react to the imbalance of pressure on the hot side vs. cold side pressure causing a reduction in flow.

What I'm getting at is I think pressure balancing has been around longer than these insta hot systems and now the old technology doesn't gel w/the new technology and a new issue has been created from this mix of technology. This is what I've heard, but have you run across similar scenarios?

 

[Master Plumber Mark]

yes they dont work well with anything

tankless will usually cause you some grief and

you sepnd the next few years trying to "tweak it"

hopeing to recoup your investment......


its only normal when you got about a 1/2 inch or less
coil for the ot side and a 3/4 cold full line fighting eash otehr through
tha tpressure balanced valve.....

then when the coil begins to lime up, its all over


http://www.weilhammerplumbing.com/houseofhorrors/

 

[Sponsor]

 

[hj]

pressure

They are pretty much about the same age. But if you select an undersized tankless heater, then the pressure loss at maximum flow will be "enormous" and the cold water flow will be diminished to match it.