1/2" PEX enough flow for whirlpool?

[mnRemodeler]

If I tee the hot and cold together (after the faucets mix the temp) into a single 1/2 uponer pex line and run that to the fill spout will I get enough flow out of the pex? I don't want it to take forever to fill the 2-person tub.

The spout I'm using is an OS&B Fill and Drain combination. It only takes 1 pipe going into it.

Logically I'm thinking that whether I run 2 lines that Tee right at the back of the fill spout or if I Tee 2 lines at the faucets and run a single line to the back of the fill spout, its going to be the same flow rate, correct? The difference between Teeing right at the back of the fill spout is the water only travels in a single pipe for a distance of about 1 inch versus about 4 feet the other way. But I have to believe water must always flow at a rate constrained by the smallest diameter and it doesn't matter where its located?

 

[Terry]

Most valves require either copper or pipe nipples to the tub spout. PEX and their fittings are too small.
If you don't have a shower head, and it's only a tub spout, then you might get by with the reduced flow to the spout. PEX is smaller than copper, and the fittings are even more of a reduction in flow.

 

[Sponsor]

 

[Terry]

Oh wait, A combination tub drain and filler?
Tub fillers below the flood level haven't been legal to use, but I see that this one is approved?
It puts out 4.2 gallons a minute. Not very fast filling.

https://osb.ca/products/product-overview/fill-drain.php

 

[mnRemodeler]

Yes that's the one that I have. I didn't do any research when I bought it. The people at Lowes recommended it.

The tub I have is a watertech 6043
http://watertechtn.com/product/6043-whirlpool-bathtub/

I have 3/4 pex run right to the framing where the tub will sit.

I have to drill holes and mount the valves on the short end of the tub. In the photo above, they would be located on the right side where the hump sticks out.

Then I have to run piping from the valves to the long side of the tub where the combination drain and filler is located. You can see that in the bottom center of the photo. So basically, around the corner from the valves. I cannot mount the valves on the tub deck (which is already tiled)

I was opting for pex as an easier install. The 3/4" supply lines would be reduced to 1/2" going to the valve. Then 1/2" from the valve to a Tee where the other valve would tie in and then a single 1/2 pex to the filler. That was the plan, anyway.

I am comfortable sweating copper.

I've not installed any of this yet so if I need to change directions now is the time to do it. This tub is in a bed and breakfast so it will be used by guests. I want to make sure it performs well and they don't have to wait forever for it to fill.

Do you recommend I consider something other than the combination drain and fill?

 

[Terry]

4.2 GPM is not very much.
How many gallons is that tub? The Delta in the picture above is 18 GPM.

 

[mnRemodeler]

The tub holds 50 gallons.

 

[mnRemodeler]

So I called the fill drain manufacturer and they told me the drain comes with aerators installed. They said if I remove them and install the full flow aerators that they sent in a bag, that it will then flow however much water my plumbing system puts out. In other words, I should expect more than 4.2 GPM providing my plumbing will put out more than that. So I guess I'm back to trying to decide if I should run copper instead of the pex? I don't know if the 1/2" pex would reduce the GPM that much more over copper that its enough to worry about?

The problem is, once this tub is installed in the concrete pad its not coming out and I won't know how it performs until after its installed. So I'm trying to do everything I can get to get the best fill rate.

The tub manufacturer is telling me that if I decide to use valves other than the fill & drain, that I will need to order the overflow and drain from them as its custom to the tub. So while I could install delta faucets, for example, to do so I'd have to order a new drain from the OEM.

So much for installing this tub tomorrow. I 'm just not sure on the wisest course of action. I hate the idea of installing it and not being happy with it. Just don't know if I'm over thinking things.

 

[Reach4]

But I have to believe water must always flow at a rate constrained by the smallest diameter and it doesn't matter where its located?

It is not the case that the smallest diameter determines the flow.

Also, some 1/2 inch PEX (F1960 such as Aquapex) has larger internal diameter for fittings than others. The ID of the pipes is the same for 1/2 inch PEX, but the fittings differ.

 

[mnRemodeler]

I'm using wirsbo/uponer pex and the propex fittings.

 

[Reach4]

http://www.uponorpro.com/calculator/ is a calculator
http://www.uponorengineering.com/~/media/extranet/files/plumbing literature/pipesizing_is_p736_0314.ashx?version=062720161015 includes use the calculator. It also says

Domestic Hot-water Piping

• Maximum velocity of 12 ft./sec. through pipe •
• Recommended velocity of 8 ft./sec. through pipe

I peak out at 6 GPM when I fill a tank via 1/2 inch Wirsbo PEX. That is also going through my water softener and cartridge filters.

That said, why not use 3/4 PEX? Being that it is a tub, either is going to fill it. 1/2 has the advantage that hot water will get to the tub sooner. But the amount of cooled down hot held in the 3/4 inch PEX will be small compared to the fill amount of water.

There also exists a compatible 3/4 PEX (F1960) to 1/2 NPT adapter, if that would be useful. https://www.menards.com/main/plumbi...npt-adapter-2-pack/p-1444442685413-c-8556.htm
https://www.menards.com/main/plumbi...npt-adapter-2-pack/p-1444442696452-c-8556.htm

http://www.siouxchief.com/products/...dapters-connectors/straight/mip-no-lead-brass http://www.siouxchief.com/products/...dapters-connectors/straight/fip-no-lead-brass

PowerPEX is the Sioux Chief brand for their F1960 things.

 

[mnRemodeler]

I can use 3/4". I have 3/4" pex already ran to the tub location. But going into the fill spout it has to be a single 1/2" connection. So my thought was that I wouldn't gain anything with the 3/4" if I have to Tee the hot and cold together into a single 1/2" fitting going into the fill spout.

Also, the valves are 1/2"

 

[Reach4]

So my thought was that I wouldn't gain anything with the 3/4" if I have to Tee the hot and cold together into a single 1/2" fitting going into the fill spout.

"Anything" is a strong word. Maybe use "much" or "a lot" instead.

What do you think about a 3/4 PEX to 1/2 NPT fitting? Worth pursuing? It depends.

 

[mnRemodeler]

I could use 3/4 PEX to 1/2 NPT fittings and 3/4" pex but again I would need to know if the end result would be a lot better flow or only slightly better or no difference from using all 1/2" pex

 

[Reach4]

I could use 3/4 PEX to 1/2 NPT fittings and 3/4" pex but again I would need to know if the end result would be a lot better flow or only slightly better or no difference from using all 1/2" pex

I would think significantly better. I was going to post a guess. I cannot back up my guess. If I could, I would need more info anyway. But I don't need more info, because I won't be attempting to calculate it. I am not a pro. My guess may have been way off.

I think the flow with 3/4 PEX would be more than for 1/2 inch copper. With 1/2 inch PEX, the flow would be less than with 1/2 inch copper.

Whichever way you go, please tell us how long it takes to fill a 5 gallon bucket with all cold and with 50% hot/50% cold.

 

[hj]

HOW LONG the smaller tubing is determines whether it will restrict the flow or not. A short piece between the 3/4 lines and spout would be negligible, longer 1/2 lines from the valves would be a different story however.

 

[mnRemodeler]

If I ran all 1/2" pex it would be 4 sets of lines about 5 feet long each. I'm starting to consider running 1/2" copper. What I worry about though is the heat from sweating them damaging something. I always use a wet rag with cold water to protect things I don't want to get too hot. But I'm not sure on the valves, for example. It may be possible they come apart and I can remove anything that couldn't take the heat.

HOW LONG the smaller tubing is determines whether it will restrict the flow or not. A short piece between the 3/4 lines and spout would be negligible, longer 1/2 lines from the valves would be a different story however.

 

[mnRemodeler]

Still wrestling with trying to make a decision. You can see from the photo that the hot water valve has a hole diameter much smaller than the 1/2 pex fitting I'm holding. To me that would mean 1/2" pex would be plenty considering the valves I have as the flow would be restricted more by the valve than the pex, would it not?

I'm debating about finding new valves that I can run 3/4 pex to the valves. But then the fill spout still only takes a single 1/2 line to feed it so I don't know if I would gain much with 3/4 valves and the larger pex lines feeding them.

 

[Jadnashua]

I would use copper from the valve to the spout. This will do two things: provide something stable to anchor the tub filler, and give you more volume. Keep in mind that while the valve may limit how much from each supply can get through, once mixed, you have the potential of a higher volume than just the one inlet. Depending on the time of the year, in the winter, you might only need to mix a little cold in, but in the summer, you'd need a lot more. Many of the valves try to use all of the hot, and make it cooler by adding some cold rather than tapering each.

 

[Reach4]

as the flow would be restricted more by the valve than the pex, would it not?

I don't know. It does seem like a mighty small port.

 

[mnRemodeler]

I think I'm going to go tomorrow and get the Delta rough-in valves. I won't use the faucet they come with. Instead I'll use just the two valves which I'll run to the fill/drain combo that I have.