Need PEX Plumbing Advice for Bath Remodel

[Jadziedzic]

Let me be specific. I have 7 2x8" floor joists at 16" OC that now have been sistered to stiffen the floor. I'll be laying porcelain tile when all said and done. How do I lay copper without weakening the joists? I will not notch. The holes need to be in the center of the joists. The only way I can see to get copper pipe through these joists is to cut it up into 14" pieces and re-assemble with several couplings and solder once in. That doesn't sound like a good plan to me.

The hole drilled in the (center of the) joist will naturally be larger than the outside diameter of the copper pipe; drill the holes large enough to accommodate "mickey mouse ear" pipe supports (I believe the trade name is "suspension clamps") and you'll probably be able to get sections nearly 25 inches long through one joist if you stick the clamps in the bored holes after the pipe is threaded through. You can also flex rigid copper tubing - not sure if that's kosher, but there *is* some flex there - which might get you one length of pipe through three joists.

 

[Houptee]

I have a 3 family house and the water meter is only 5/8, with 1" copper to the house.
Once it emerges in the crawl it was reduced to 3/4" copper with 1/2" branches all over the place with rusted gate valves that had no handles left on them, all corroded.
I tore it all out and put a new 1" ball valve with waste, then ran 1" pex direct to the mechanical room, then Tee'd off in 3/4 pex to separate each apt. So starting from the mech room, Hot/Cold all in 3/4 Pex then back under the house to under the kitchen areas with a 3/4 straight thru mini manifold with 1/2 branches, then continue onto the bathroom areas with a 3/4 end stop mini manifold 1/2 branches. Works so much better than the old setup pressure wise. And now I can shut off each apt in the mech room, no need to crawl under the house looking for the old corroded vales.
Since the water meter is only 5/8 I was surprised the pressure and volume is adequate for 3 units but it has always been fine.
So to me 1" pex sounds a bit overkill unless you have some kind of huge shower with multiple heads?

 

[Sponsor]

 

[Mathelo]

Mathelo, I don't think anyone has boo-hoo'd you suggested use of PEX. It's your idea of using a manifold supplied by a 3/4" line that has branches of both 1/2" & 3/4" that had me questioning your method. That's just a bad idea, and why you wont find a manifold built that way. As far a using 1/2 or 3/4 to you shower, we just don't have enough information to give you an answer. If you are installing a multi head shower, run 1" PEX (eq. to 3/4" copper) to the shower, and tee off of it with 1/2" PEX to everything else. You'll be fine. My house is plumbed with copper trunk & branch, and when I am in the shower in the AM & I feel a slight & momentary drop in pressure, no change in temp though, because I have a pressure balancing valve, It gives me a warm fuzzy feeling because I know my wife is up & at the kitchen sink making the coffee.

Jim,

Thanks for this reply. The lack of available manifolds for what I was requiring made me wonder if I had this all wrong but it is still not clear to me why a manifold with both 1/2" and 3/4" branches is a bad idea. Can you (anyone) explain to me why this is a bad idea, a manifold with both 1/2" and 3/4" branches? At this point I'm likely to make a change in my plans to trunk and branch but I'd like to understand why the manifold wouldn't be more effective.

I've included a transparent image of my floor plan looking down on the second floor through the basement with the plumbing more or less as it is currently. The baths are directly over the hot and cold water supply in the basement, about a 50' run and the kitchen / laundry room area is at the other end of the house but, of course, on the first level. Both baths currently branch off of the same 3/4" trunk. I'm thinking I need to at least give these two baths separate lines with 3/4" to each shower. Additionally, the master bath will have two shower heads and no tub. Not massive shower heads but something bigger than normal. The hall bath with have a single shower head, again not extravagant but larger than normal.

Hopefully this helps.

Louis

 

[Jim Mills]

Bet it takes forever to get hot water to the kitchen. Wonder why they didn't run the trunk lines down the middle of the house. If you have a manifold supplied by 3/4" pipe with both 1/2" & 3/4" branches, the 3/4" branches would cause the pressure to drop to the fixtures running off 1/2" while in use. Not exactly how a manifold system is suppose to work. Hell, if you have both those showers going at the same time, you may get just a dribble at the kitchen sink.

 

[Mathelo]

Bet it takes forever to get hot water to the kitchen. Wonder why they didn't run the trunk lines down the middle of the house. If you have a manifold supplied by 3/4" pipe with both 1/2" & 3/4" branches, the 3/4" branches would cause the pressure to drop to the fixtures running off 1/2" while in use. Not exactly how a manifold system is suppose to work. Hell, if you have both those showers going at the same time, you may get just a dribble at the kitchen sink.

Jim,

I think I now understand the concern with mixing different branch sizes at a manifold. It effectively creates a pressure imbalance. Having said that, I believe the showers should get priority so I'm not sure that imbalance would bother me and in fact might be a good thing. I wonder? In any case, running 3/4" or 1" to the showers and using 1/2" branches for the other fixtures should maintain that pressure differential for the shower.

Do you agree that each bathroom should have its own 3/4" or 1" line? The master bath will have two shower heads but no tub. Or maybe I just need to run a 1" line for both baths, branch off 3/4" for the showers, and then branch off again with 1/2" for the sinks and toilets.

I suspect the route to the kitchen is based on the original floor plan, which was considerably different than now, i.e., original had one faucet and no dishwasher. I've also not shown the two outside faucets on the front of the house, which might support the current route as most efficient in terms of pipe usage. We are not as conscious of low water pressure in the kitchen because we aren't "under" the water but it does take awhile to get hot water to the kitchen sinks. This may be a good application for a hot water recirculating pump.

Personally, I find the plumbing in the house to be a messy maze of pipe. I've got a boiler supporting a mix of baseboard heat (basement) with hydronic forced air and radon treatment - both were retrofits. Maybe I should just re-plumb the whole thing!

Louis

 

[Mathelo]

I have a 3 family house and the water meter is only 5/8, with 1" copper to the house.
Once it emerges in the crawl it was reduced to 3/4" copper with 1/2" branches all over the place with rusted gate valves that had no handles left on them, all corroded.

I hate those gate valves. They are just a leaky corroded mess. I have several that I'm going to ultimately replace with ball valves.

I tore it all out and put a new 1" ball valve with waste, then ran 1" pex direct to the mechanical room, then Tee'd off in 3/4 pex to separate each apt. So starting from the mech room, Hot/Cold all in 3/4 Pex then back under the house to under the kitchen areas with a 3/4 straight thru mini manifold with 1/2 branches, then continue onto the bathroom areas with a 3/4 end stop mini manifold 1/2 branches. Works so much better than the old setup pressure wise. And now I can shut off each apt in the mech room, no need to crawl under the house looking for the old corroded vales.
Since the water meter is only 5/8 I was surprised the pressure and volume is adequate for 3 units but it has always been fine.

So to me 1" pex sounds a bit overkill unless you have some kind of huge shower with multiple heads?

Two shower heads in the master bath. They will not be those crazy large rain shower heads but still larger than normal. So worse case scenario would be three shower heads or two shower heads and a tub.

Louis

 

[Jim Mills]

I refer to my original post. You are way over thinking this. There are arguments for and against almost every way you can lay pipe. Follow sound principles for whatever method you choose, and you will be just fine. I'm a "trunk & branch" Guy. Younger guys like manifolds & home runs. They both accomplish the same thing when done correctly. A home run with 1/2" will get hot water to the fixture a second or two faster. There ya go...
The size of the shower head is not the only factor. Just because it's bigger doesn't necessarily mean it has a higher GPM rating. Maybe the jets are just spread out further. And what shower valves are you using? Some are rated higher than others. How often do you think you will be using all three showers at the same time anyway? And can your well system and water heater support this easily?

 

[Mathelo]

I refer to my original post. You are way over thinking this. There are arguments for and against almost every way you can lay pipe. Follow sound principles for whatever method you choose, and you will be just fine. I'm a "trunk & branch" Guy. Younger guys like manifolds & home runs. They both accomplish the same thing when done correctly. A home run with 1/2" will get hot water to the fixture a second or two faster. There ya go...
The size of the shower head is not the only factor. Just because it's bigger doesn't necessarily mean it has a higher GPM rating. Maybe the jets are just spread out further. And what shower valves are you using? Some are rated higher than others. How often do you think you will be using all three showers at the same time anyway? And can your well system and water heater support this easily?

Over thinking? Me?

Planning on using the Hansgrohe 3/4" valve.

I don't expect all 3 showers to be used at the same time all that often. Really a worse case scenario.

And yes, my well is slow but the radon system does provide me some buffer on water usage for a few minutes. Just not continuous.

Water heater should not be a problem.

Louis