Plumbing expertise needed.

[Attempts Plumbing]

Hello!
I recently bought an older home and while the home inspector said there was a "flow issue to the shower" I don't think he fully captured the level of "the issue" which is down right terrible... After taking a look in the basement I see that that 90% of the pipe is galvanized and very rusted at least on the outside and uselessly complex, hacked and slashed together with random pipes capped and lots of elbows throughout system which looks like it's been "customized" over the last 50 years of the home's 100 year life.

This being the case and doing a bit of reading I've decided to replace it all with pex for a handful of reasons. Cost, DIY'ability, ease of install, and future upgrade potential. Not knowing much about plumbing I have a few questions about Pex, line size, pressure, and best practices.

The house has all of it's water fixtures on the north and south side. I am thinking about running a dual manifold system, north and south, and break out to each node with 1/2 pex-b. The main comes in the north side and the hot water heater is on the south side of the home, I am planning on running cross connect (3/4 pex-b hot & cold) between the two manifolds and 1/2'' to each of the nodes or to easiest node connection point leaving the newer copper where it looks good.

Few questions I have:

1. Does the size of my cross connect matter?
   1. I wanted to use pex-a at 1" in hopes that the extra flow capacity and flex would give me more of a buffer or capacitor effect to stop pressure drop off and/or shower cold spots, but opted against it in this iteration for water savings vs comfort. Logical?
2. It it worth while to branch off the manifold for each of my nodes in the kitchen and replace lines where there is a "T" ie, the sink hot line to the dishwasher, and "T" from the washer to dryer?
   1. To keep everything uniform i would love to have a line from the manifold to each node but cost vs performance is where i am under educated.
3. Is the overall design viable from a plumbers / code / usability perspective.
   1. I am not a plumber and a spot check would ease my mind and help plan final equipment purchases.
4. Would it make more sense to "single flow" the whole system?
   1. instead of "T"ing the cold out in the bathroom and closing that run, to move the cold cross connect to the end of that run then go to the hot water heater? In this model main in would be a continuous run from main to the bathroom hot line closure.

Thanks in advance for any and all input!
Cheers,
Jason

 

[Diehard]

Hello!
I recently bought an older home and while the home inspector said there was a "flow issue to the shower" I don't think he fully captured the level of "the issue" which is down right terrible... After taking a look in the basement I see that that 90% of the pipe is galvanized and very rusted at least on the outside and uselessly complex, hacked and slashed together with random pipes capped and lots of elbows throughout system which looks like it's been "customized" over the last 50 years of the home's 100 year life.

This being the case and doing a bit of reading I've decided to replace it all with pex for a handful of reasons. Cost, DIY'ability, ease of install, and future upgrade potential. Not knowing much about plumbing I have a few questions about Pex, line size, pressure, and best practices.

The house has all of it's water fixtures on the north and south side. I am thinking about running a dual manifold system, north and south, and break out to each node with 1/2 pex-b. The main comes in the north side and the hot water heater is on the south side of the home, I am planning on running cross connect (3/4 pex-b hot & cold) between the two manifolds and 1/2'' to each of the nodes or to easiest node connection point leaving the newer copper where it looks good.

Few questions I have:

1. Does the size of my cross connect matter?
   1. I wanted to use pex-a at 1" in hopes that the extra flow capacity and flex would give me more of a buffer or capacitor effect to stop pressure drop off and/or shower cold spots, but opted against it in this iteration for water savings vs comfort. Logical?
2. It it worth while to branch off the manifold for each of my nodes in the kitchen and replace lines where there is a "T" ie, the sink hot line to the dishwasher, and "T" from the washer to dryer?
   1. To keep everything uniform i would love to have a line from the manifold to each node but cost vs performance is where i am under educated.
3. Is the overall design viable from a plumbers / code / usability perspective.
   1. I am not a plumber and a spot check would ease my mind and help plan final equipment purchases.
4. Would it make more sense to "single flow" the whole system?
   1. instead of "T"ing the cold out in the bathroom and closing that run, to move the cold cross connect to the end of that run then go to the hot water heater? In this model main in would be a continuous run from main to the bathroom hot line closure.

Thanks in advance for any and all input!
Cheers,
Jason

Appears to b e a reasonable approach. I believe the multiple manifold use is the preferred method in many applications.
To give you an idea of difference between 3/4" and 1" you can look at the chart below and compare.
Of course the big factors are flow rates and distance. The chart is based on 100 feet so the actual pressure drop would be less when distance is less. For example 30 feet of tubing would be about 1/3 the posted value.
Also fittings such as elbows and tee branches would generally be equivalent to about 15 to 20 feet of pipe.

 

[frodo]

View attachment 20994

 

[Attempts Plumbing]

Thanks for the replies and info! @frodo I was planning on building my own manifolds out of equal length of pex nailing it to a board and using ball valves to control flow to each node. But i may need to refactor that, after what @Diehard mention on elbows and T's affect on line pressure (thanks for the info there.)

@frodo what kind of thermal loss would I expect from going with re circulation (more dollar value vs BTU's)? It seems that having hot water continuously moving through pipes could keep my water heater running more often and from wall to wall it's only 36'10" so it may not be worth the convenience...?

Thanks for the information it is much appreciated and I will for sure incorporate your input, thanks again!
Cheers,
jason

 

[frodo]

Thanks for the replies and info! @frodo I was planning on building my own manifolds out of equal length of pex nailing it to a board and using ball valves to control flow to each node. But i may need to refactor that, after what @Diehard mention on elbows and T's affect on line pressure (thanks for the info there.)

@frodo what kind of thermal loss would I expect from going with re circulation (more dollar value vs BTU's)? It seems that having hot water continuously moving through pipes could keep my water heater running more often and from wall to wall it's only 36'10" so it may not be worth the convenience...?

Thanks for the information it is much appreciated and I will for sure incorporate your input, thanks again!
Cheers,
jason

I wire the circ pump to the light switch in the bathroom
when you turn the light on the water circulates
when you turn it off it stops
It is more of a convenience than anything else
36' of 3/4 pex is right at 1 gallon of water volume [estimated]

 

[fixitron]

I am curious why you are using PEX-b on the 1/2" pipe and PEX-a on the larger pipe?
PEX-a should only be used with expansion fittings and the PEX-b can only be used with crimp or compression fittings.

As for thermal losses, it is always a good practice to insulate water pipes- hot water pipes will lose less heat to the air around it and cold water pipes will not "sweat" when it is warm and humid.

 

[Diehard]

I didn't notice the reference to PEX-A. I think it's overkill, for the potential flow rates, distance and number of fittings.
Also, I would not be too concerned with the use of a branch Tee, regarding the 20 feet or so of equivalent pipe length. That would be with the average flow rate for one fixture, the 20 feet equivalent pipe length wouldn't amount to enough to worry about. Assuming you have average water service pressure, you will not be losing excessive pressure anywhere.
Just the absence of the traditional globe valves alone, will save you a substance amount of pressure losses.