Need some advice with a custom built manifold

[Rsaybe]

Hello, I have a question. I'm putting together a copper pipe manifold to separately distribute some of my water lines throughout my house.

My main supply line is 3/4" and plan on having 1/2" ports for the branches. I'm building the manifold out of tees as I need particular spacing between each branch. The question is, should I use 1" tees with 1/2" branches for better flow of redirection?

So I would transition the 3/4 main to a slightly larger copper body (the 1" tee) for the manifold section.

Or would it be best to keep the main body of the custom built manifold the same size as the main line using the 3/4" tees with 1/2" outlets for the branches?


Any suggestions on which would be best? Looking for the best possible flow without any loss of pressure. Will be soldering all the joints.

 

[Fitter30]

What type of pipe?

 

[Sponsor]

 

[Rsaybe]

Hello, I noted that in the beginning of my post. Will be putting together a copper pipe manifold. Will be using copper pipe.

 

[Jeff H Young]

In normal plumbing with copper you would never ever increase the pipe main size to 1 inch , But there reasons oddball uncommon unconventional reasons why increasing to 1 inch might make sence , but ive never found a need to and if you arent going to say why for example that the 3/4 is actually undersize then Just build with 3/4 x3/4 x1/2 tees there just has been no reason given to concider 1 inch so no dont bother

 

[Reach4]

I was thinking that I would increase to 1 inch for the body of my manifold, but then I saw the difference in the prices for the bigger copper..

https://www.supplyhouse.com/sh/control/search/~SEARCH_STRING=reducing%20copper%20tee

 

[Fitter30]

Google sweat copper manifold sure there cheaper than fitting. Since we don't know how many outlets. 1" X1" X1/2" tee is $6+

 

[Rsaybe]

I have specific requirements were i need certain spacing due to joists running along the area. Those ready made manifolds would be a nice option however having them branches evenly spaced isn't ideal for my setup. For this reason custom building the manifold will be best. This will be setup in our crawl space.

I'm not too concerned with the initial cost for the tees, it's a one time drop and done.

What got me wondering if up-sizing (only the manifold portion) was a better option is that I saw Sioux Chief offering copper manifolds with 3/4" inlets and 1/2" branches on 1 in trunks. The manifold itself was 1 in pipe although the inlets were for 3/4" pipe.

Example Showing the 1" trunk with 3/4" Inlet

Seemed like this was designed that way for some purpose?

 

[Fitter30]

I have specific requirements were i need certain spacing due to joists running along the area. Those ready made manifolds would be a nice option however having them branches evenly spaced isn't ideal for my setup. For this reason custom building the manifold will be best. This will be setup in our crawl space.

I'm not too concerned with the initial cost for the tees, it's a one time drop and done.

What got me wondering if up-sizing (only the manifold portion) was a better option is that I saw Sioux Chief offering copper manifolds with 3/4" inlets and 1/2" branches on 1 in trunks. The manifold itself was 1 in pipe although the inlets were for 3/4" pipe.

Example Showing the 1" trunk with 3/4" Inlet

Seemed like this was designed that way for some purpo

Build your manifold then can use globe valves instead of circuit setters for balancing. Valves piped in the bottom out the top very small adjustment will make a big change. Globe valve is about the only one once it is set flow doesn't change.

 

[Jeff H Young]

I have specific requirements were i need certain spacing due to joists running along the area. Those ready made manifolds would be a nice option however having them branches evenly spaced isn't ideal for my setup. For this reason custom building the manifold will be best. This will be setup in our crawl space.

I'm not too concerned with the initial cost for the tees, it's a one time drop and done.

What got me wondering if up-sizing (only the manifold portion) was a better option is that I saw Sioux Chief offering copper manifolds with 3/4" inlets and 1/2" branches on 1 in trunks. The manifold itself was 1 in pipe although the inlets were for 3/4" pipe.

Example Showing the 1" trunk with 3/4" Inlet

Seemed like this was designed that way for some purpose?

if you size by the book you should be good. if you know 3/4 is too small the 1 inch manifold might maybe help whether it will be noticeably better I cant guess it cant hurt that I know of

 

[John Gayewski]

I would use 1". You may need more in the future. If you were gonna rib a line to fill a pool or something bigger pipe would help.

 

[Jeff H Young]

I dont think the post was talking about increasing pipe size sounds like he was taking a 3/4 line increasing the size for like a foot section or 2 ft and a bunch of 1/2 inch branches a larger manifold on a smaller main

 

[Rsaybe]

Yes, that is correct, the manifold section will only be about no longer than a foot or two. The increase in pipe size from 3/4" to 1" was only for the manifold section.

My main municipal supply line comes into my home at 3/4 in with very high pressure at almost 90 to 95 psi. I actually installed a watts pressure reducing valve some time ago and brought the pressure down to around 75psi.

I thought the 90psi was too much for some of our appliances. Didn't want to risk any premature failures.


I was hearing that it may be a good idea if we came off the manifold at 3/4" (instead of the 1/2 in branches) and continue until I'm below the fixtures (toilet, sink, shower) and then do the 90 degree and transition to 1/2" from there.

This would reduce friction and decrease velocity thus resulting in lower pressure friction drop, which can potentially lead to higher pressure at the fixture outlet.

Does this sound correct and or like a better approach?

 

[Reach4]

If you change stuff, 1 inch after the PRV until where the cold and hot diverge would be an improvement. Pressure drop after the PRV is more of a consideration than before the PRV. I would not retrofit for just that.

3/4 out of a hot manifold, such as for a single bathroom hot, would make you wait longer for hot water than 1/2 inch would.

 

[Jeff H Young]

unless youve undersized your piping there is no reason to concider your plan you are reinventing the wheel are you trying to mickey mouse correct a problem ? and understandably you are trying to cheat rather than do it the right way ? Ive been there but otherwise its silly or im not following you

 

[Rsaybe]

The only reason I was considering it is due to some other forum member that mentioned running 3/4 in branches from their manifold and upturning 90 degree to each fixture with 1/2 in pipe. The talk seemed to be more about the importance of volume since I already have sufficient pressure.


This was their theory, ---> "A smaller pipe will deliver less volume than a larger pipe. You will have the same pressure as incoming. More water moving means hot water will reach the appliances faster, and more equally than with a smaller pipe. Too much demand on a smaller pipe will result in lower volume being produced."


I'm replacing an existing tub with a shower along with a sink/vanity. There will be two separate shower heads installed. One on each side of the wall with separately controlled valves along with a 12 in rain shower head coming down from the ceiling.

I would like to make sure we have good flow with sufficient pressure coming off those shower heads.

I have also had situations with our existing single water line (trunk & branch) whenever the hot kitchen faucet gets turned on it takes some hot water from the shower. The kitchen sink is on the opposite side of the bathroom wall.

We have a second bathroom in the backside of the house about 40 ft of pipe away. This second bathroom can take a good 1-2 minutes for hot water to flow through the tap.


With that said, were you suggesting it would be best to come off the manifold at 1/2 in as opposed to 3/4"?

So coming into a 3/4" manifold (same size as out main city supply line) and branch out at 1/2" lines to each fixture? And not branching out at 3/4" off the manifold as far as I can and then turn up with 1/2" to each fixture?


I just want to make sure I'm doing this correctly using the best possible method.

 

[Reach4]

More water moving means hot water will reach the appliances faster, and more equally than with a smaller pipe.

I specifically disagree with that one.

Pressure to you seems to mean static pressure. With more flow, a bigger pipe delivers more pressure to the fixture.

If you have a backwashing filter, you want a big path to that.

 

[Slomoola]

Running 3 heads in one shower doesn't take a lot. 1" pipe flows 15 gallons per minute. Not talking about PEX B either. Copper or irrigation pipe which you won't be using. PEX A is close to copper size for size but not the same. Copper is still the king.

Most shower heads only flow like 1.5 or a max of 2.5 GPM. I always remove the water restrictors for more gundy.

I plumed my house in 2 halves. Also have 2 hot water tanks. 1" PEX A to the back side of the house. 3/4" PEX A to showers and all exterior faucets. 1/2" PEX A to all sinks and toilets. My PRV is set on 56PSI. Got plenty of water.

From Google

A 3/4-inch copper pipe typically flows between 6 and 12 gallons per minute (GPM) in a residential setting, though the exact flow depends on the specific conditions of the plumbing system

• Water Pressure: Higher water pressure (PSI) results in a higher flow rate.
• Pipe Length: Longer pipes have more friction loss, which reduces flow rate.
• Fittings and Valves: Elbows, tees, and valves all create friction loss, decreasing the GPM.
• Water Velocity: To prevent pipe erosion and noise, flow velocity should generally be kept below 5 to 8 feet per second (ft/s). The flow rate to maintain this limit is around 6.5 GPM (at 4 ft/s) to 10.9 GPM (at 8 ft/s).
• Pipe Condition: Mineral buildup or corrosion inside older pipes can significantly restrict flow.

 

[Rsaybe]

With more flow, a bigger pipe delivers more pressure to the fixture.

So then coming off the 3/4" manifold with 3/4" branches as far as I can and then turn up with 1/2" to each fixture?

Is this what your saying would be a good way to do this?

 

[Rsaybe]

Running 3 heads in one shower doesn't take a lot. 1" pipe flows 15 gallons per minute. Not talking about PEX B either. Copper or irrigation pipe which you won't be using. PEX A is close to copper size for size but not the same. Copper is still the king.

Most shower heads only flow like 1.5 or a max of 2.5 GPM. I always remove the water restrictors for more gundy.

I plumed my house in 2 halves. Also have 2 hot water tanks. 1" PEX A to the back side of the house. 3/4" PEX A to showers and all exterior faucets. 1/2" PEX A to all sinks and toilets. My PRV is set on 56PSI. Got plenty of water.

I'm not so much concerned over the amount of time it takes the cold water (that's been sitting in my pipe) to flush out as much as with having the necessary pressure I receive at the fixtures. Particularly the shower fixtures.

I would much rather have pressure I can feel while under the shower heads. Will also likely remove the water restrictors. I'm in California and just about everything sold for shower fixtures have some serious limiting restrictors installed reducing the flow on shower heads, rain heads and handhelds.


I also like to note that one of the shower heads is coming from a shower panel which has several jets.


So coming off the manifold at 3/4" and going as far as I can and then changing to 1/2" right below each fixture would be a good plan?

 

[Reach4]

I would take into account where I am going. Cold water manifold? Sounds good. Hot water manifold, I would come off with 1/2 except for a big tub. I am not a pro.