Help with water supply lines in back to back bath.

[Timski]

Do you guys have any concerns with the current Hot and Cold supply line setup in this back to back bathroom. The shower and Sink both share the same 1/2 supply lines. I would think that if the sink in the one bath is used it would rob pressure from the shower. We havent moved into this house yet so i am not sure how the current set up affects pressure.

The current order on the Cold supply line is toilet > sink > shower. The shower and Toilet are both for the back bathroom.
Hot supply line is sink > shower

Should I tee in the Shower below the toilet and sink?

Where should i add air chambers? ive seen some added both high and low.

3rd photo is the current set up color coded for H/C
4th photo is a possible sketch, the green is for possible air chambers in either high or low locations.

 

[Jadnashua]

If you have 1/2" lines feeding the bathrooms, you'll be glad you have pressure balanced shower valves! You'll be starved for volume capacity. While pressure and volume are related, they are not the same thing. A showerhead only accelerates the water (Bernoulli principle) when there's actually a restriction...that means, there's more water trying to get through than it can normally flow. It's that acceleration that you notice making the shower feel better, not the volume. But, if there's not enough volume, you don't get the acceleration, and it dribbles out; the same effect you see if you have a rain shower head...lots of holes, no restriction, no acceleration, but the same volume.

Generally, it's good practice to run 3/4" or larger supply lines to the bathroom, then branch off to 1/2" for the various fixtures. It depends on how many fixtures you expect to be running at the same time, how large the supply line should be. You might need more, but then, most residential WH don't have that large of inlet/outlet ports.

Using copper, the Copper Institute's guidelines say to not run the hot water faster than 5fps, and on a 1/2" line, that's only 4gpm, not enough to feed two showers in the winter when you'll be using less cold to temper it. Conversely, a 3/4" line can flow double that at that same 5fps velocity. They allow 8fps on the cold lines.

Typical tub filler: 5-6.5gpm
Typical showerhead: 2.5gpm
Typical sink: 2.2gpm

 

[Sponsor]

 

[Timski]

I need to update this a bit.

So we have 3/4 lines that feed to the upstairs. From there the shower/sink in question share a 1/2 line off the 3/4''

I filled a 5 gallon bucket from the bath tub spout in under 1 minute. I also put a pressure gauge on washer line and it was reading 59psi without any water flow.

Now the water lines need to move to the left to accommodate a new sink that is off set from the current set up. Do you see any flow or pressure issues by me using 1/2 pex from the floor to feed the shower and sink at the same time? I know the pex fittings are a bit more restricted but i was sure how it would affect.

Since this shower and sink are both on the same 1/2'' copper line off a 3/4'' line below the floor i have some sudden flow/pressure drop concerns if i am using the shower and my kids are using the sink (sink off and on) on the other side of the wall. Should i be worried or should i stop worrying?

Attached are 3 Photos 1st you can see what fixtures share a 1/2 line out of the floor
2nd is the how the 3/4 feeds the upstairs in to 1/2. 3rd is how i currently am stubbed out of the floor with 1/2.

Thanks again.

 

[Jadnashua]

You'll probably notice the decrease in flow at the shower if it's sharing the same 1/2" line, but unlike before anti-scald tech was introduced and required, it won't give you a burst of cold...it will just decrease the flow on both the hot and cold proportionally, so the temp should stay about the same. It would be better if the tub/shower got its supply from the 3/4" line rather than sharing the 1/2" with the sink. Pex allows higher velocity to help compensate for the smaller ID, but that does increase the friction and thus a decrease in the working pressure. Static pressure will remain the same. How much it will affect things depends on how long the lines are, and how many fittings you need. NOte, expansion fittings with PEX-A have smaller restrictions than crimp connectors.

 

[Jeff H Young]

its a shower only so flow at head is restricted the faucet has a water saver too. this is old work if there is a problem concider upsizing. If you are concerned with the age of the copper and absolutly never want to mess with plumbing again concider putting new 3/4 to lav then reducing. if you like plastic rip out and put plastic.
But I dont see the half inch as a problem in itself if it was a shower only we wouldnt be discusing this and a lav is the least fixture units of everything in a house very minor undersize if that had it been a tub or tub /shower it would technicaly be more undersize.