Small PEX inlet ID on Delta R10000-MFWS

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Grizzle

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Hello All, this is my first post. I want begin by saying thanks for everyone's contribution to this awesome site.

I recently bought a Delta R10000-MFWS for a remodel - it has the 1/2" propex inlets built in. Upon inspection, the inner diameter of the inlets are considerably smaller than any 1/2" propex fitting I've seen - and measured .314" with a caliper.

My concern here is reduced flow rate while filling a tub, or running a large rain shower head.

Does anyone have any experience with these valve bodies, or data on what kind of GPM to expect? I couldn't find any data or tables with a spec of .314 ID pipe.

I'll reach out to Delta as well, but the specs and Q&A I've see on their site are vague, unless I'm looking in the wrong place.

Thanks,

- Grant
 
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Terry

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Pictures can be uploaded that are 800 pixels or less. Can I ask if you were linking your photos? Some aren't showing up, and I would like to figure out why.

The cartridge has pretty small passage ways too. The tub spout will get either 1/2" copper or 1/2" pipe nipples. You can't run PEX for the tub spout location. You can use PEX for the shower head, as those are restricted anyway. You should be getting five plus gallons a minute or more from a tub spout.

moen-tub-outlet.jpg


pex-to-copper-fitting.jpg
 
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Grizzle

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Hi Terry - thanks for the quick reply. Yes, I was trying to link pics from my google drive.

For the tub outlet, would a 1/2" FPT to propex adapter to a propex drop ear elbow with 1/2" FPT for the spout not be best practice?

Here's another try for an image:
 
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Terry

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The best practice is to follow their directions. When they say not to use PEX fittings for their spout that's pretty much what they mean. It forces water upward and out of the showerhead while filling the tub.

delta-tub-spout-install.jpg
 
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Jadnashua

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You need to learn to solder to get the valve to spout connection (unless it is threaded, then you could use brass nipples and fittings)...the rest can be in pex.

For a short distance, forcing a fluid through a smaller opening (venturi effect), the fluid speeds up through the restriction, then slows back down again without a lot of losses. If that narrowed length is long, then it starts to have serious impacts on the volume that can flow and also restricts the pressure because of the added friction.
 

Grizzle

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Terry and Jim,

The valve body does have threaded outlets which can also receive 1/2" copper. I now understand what you're both saying about reducing the flow on the outlets, and how a smaller outlet pipe or fitting (ie: for PEX) to the tub spout could force water back up to the shower head - makes sense.

Also, after reading it more closely, the installation guide does specify copper or iron pipe for the tub drop (not PEX). I was actually planning to do some soldering on the repipe of this house anyhow.

This said, if the cartridge passageways are also small, then maybe the small ID of the PEX inlets aren't something to worry about (since PSI will ultimately determine the flow more than the smaller size of the inlet)?

I'll update with any info I get back from Delta on this specific valve body.

Thank you both, and special thanks to Terry for pointing out that I should RTFM on my first post!

- Grant
 

Jadnashua

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The ID of pex is smaller than the equivalent size of copper. The Copper Institute has guidelines on the maximum flow rate in copper (5fps with hot water and 8fps with cold). Pex allows a higher flow rate, which is why it sometimes can flow the same volume of water as copper. But, if you run your pex with the same methodology as copper...i.e., fittings to change directions verses smooth bends possible with pex, the smaller ID of pex can limit the flow. 5fps in 1/2" copper equates to 4gpm. Mix that hot with some cold, and a 1/2" valve, if you limit it to the guidelines max flow rate, might get you 6gpm after mixing in a valve. A 3/4" copper supply can deliver twice the volume at the same flow rate. Yes, you can get more, but it can create some issues of flow noises, and long-term, literally wearing the pipe out from the inside. So, a smaller opening in the valve isn't necessarily an issue, up to a point.
 

Grizzle

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To follow up:

I traded the Delta valve with the shutoffs for the model without, and the ID of the PEX inlets are indeed larger on the model without the shutoffs.

My solution for providing an unrestricted connection to the tub spout was brass fittings which increase the size of the pipe between the valve and drop ear to 3/4" PEX. The drop ear outlet is still 1/2", to accept standard spout installation.
 
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