PEX & minimizing the number of fittings

[R.E.]

I've used PEX a few times as a DIY homeowner. I recently came across a few videos that show installations where numerous fittings were used in PEX runs, which I believe is contrary to the great benefits (in terms of reducing installation time, reducing the potential for leaks, maintaining flow/pressure, and lowering cost) of PEX. Am I missing something, or are these installations showing sub-optimal use of PEX?

https://ecoinnovation.ca/drain-water-heat-recovery-resources/installation/

 

[Helper Dave]

These aren't really bad examples. The 2nd video, especially, seems to make use of a few more 90s in order to keep the installation in the wall (if they'd ever finish the wall, that is). The first video is more an example of preference, I'd say. There's aesthetic vs function with PEX in some areas. A lot of people think the straight lines still look better, as with other types of piping. Others don't mind the curves here and there. All up to the installer and home/business-owner how it looks.

 

[wood4d]

I use pex just like copper, straight runs, elbows, one nailers to hold it in place. pretty freeze resistant. Better than m copper with wells, works great near the beach. I use copper in my own home but only because Im a plumber.

 

[Mitchell-DIY-Guy]

These are not really good examples of the use of PEX vs copper. They are both videos of what are called "Gray Water Heat Exchangers" which use the heat from the waste water in your shower to pre-heat the cold water going into your hot water tank. The latter isn't even available yet.

I've always schemed that these are great ideas, but not certain if code permits them in the USA. You cannot have to possibility of co-mingling waste water with fresh water, and heat exchangers do fail now and then. I can fully imagine using these, but cannot imagine buttoning them up into a wall.

 

[Diehard]

I agree! They would have to be what is called, Double walled.
I have noticed a lot of design arrangements for hydronic heating system where a simple heat exchanger is used for heating with a potable HW source. The ones that are using antifreeze cannot use single wall heat exchangers.
My experience in Mass., and I'm sure it applies elsewhere, has been that a double wall heat exchanger is required, when the fluid being heated with potable water is a high hazard or in this case, the other way around.

Typical code verbiage...
"Double-wall heat exchangers shall separate the potable water from the heat-transfer medium by providing a space between the two walls that are vented to the atmosphere. "

 

[Mitchell-DIY-Guy]

Right @Diehard, and if you have a double wall heat exchanger my guess is the efficiency is low.

I used a very efficient plate heat exchanger to heat some rails on car wash equipment; the car wash supplier was going to install yet another heat source to provide heat for the gallons of antifreeze running through them. Nothing doing I said! I already have a 1.2M BTU boiler for the hot water and a 500K BTU boiler for the floor heat, I'd be damned if I'm going to get another one. So my plumber rigged up this 40K BTU plate heat exchanger with a small pump. Worked like a charm, but it was NOT on a potable water source.