supply line diameter


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Old 03-11-06, 02:40 AM
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supply line diameter

Greetings! I'm redoing much of the plumbing in my old house, changing galv to copper. I have a bathroom on the second floor, a kitchen on the main floor, and another bathroom in the basement. Previously I had water pressure problems with the second floor bathroom. The supply line entering the house is 3/4. My question is whether there are any benefits/minuses to using 3/4 as the "trunk" with 1/2 branches to each fixture, or whether I should stick with the 1/2 size that was previously used throughout? A friend who has done some plumbing suggested 1/2 throughout, but that doesn't make sense to me given the water pressure issues, etc. Thanks in advance for any help!
 
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Old 03-11-06, 06:27 AM
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Not Enough Information

You don't supply enough information to make a determination.

Supply pipe sizing needs to be based on your home's entire water needs and ciucumstances.

You need to know and adjust for:


-static service pressure at the street supplied by the utility or well tank pressure

-difference in elevation from water source to highest water supply output in house

-if a pressure reducing valve is present

-pressure losses from the presence of backflow preventers, water filters, water softeners, etc...

-pressure losses from special plumbing fixtures such as temperature balanced showers, flushometer toilets etc...

-the maximum developed length of pipe from supply to most remote fixture

-etc...

Only after calculating pressure increases and decreases, the developed lengths of pipe, and the number of water supply fixture units for the house and a whole and for individual branches can the pipes be proeprly sized.

Anything else is just guesswork.
 
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Old 03-11-06, 06:36 AM
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pipe size

Don't listen to you friend, the other post has the answer.
 
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Old 03-11-06, 07:45 AM
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I don't know the static pressure, and not sure how to determine it.

Here's what I do know...

--elevation is approximately 15 feet
--no pressure reducing valve is present that I can tell
--there are no water filters, water softeners...I don't know what else to look for as far as backflow preventers
--there are no special plumbing features...basement bath has toilet, sink and shower....kitchen has sink and dishwasher...upstairs bath has toilet, sink and bathtup/shower
--house is small, so the maximum developed pipe length from supply to most remote feature is 25-30 feet

At this point, even a guess would be helpful since I'm contemplating using a plumber...and my experience with local plumbers has been so poor that I'd like to have a guess...and then I can ask them to explain why they would do differently, etc. My experience with local plumbers is that whatever is the cheapest approach is the one taken unless I specifically ask them to consider something different.

Thanks for any input
 
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Old 03-11-06, 10:58 AM
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How about this?

Run 3/4" cold and 1/2" hot to the bathroom.
Run 1/2" cold and hot to the laundry and also to the kitchen.
Run 3/4" cold to the water heater.

Run 3/4" until only 2 branches remain.


Where is the pressure problem now?
 
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Old 03-12-06, 07:07 AM
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If you don't want to go through the calculations, a ball park figure is to run 3/4 near the fixtures and branch to 1/2. Most codes that I deal with require 3/4 mim. on your main line.
 
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Old 03-12-06, 08:28 AM
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Most new lines I have run are 1" from the supply (well or city main) to the meter (unless it is in a meter box at the street) and then a 5/8" meter and 3/4" copper runs throughout the house with 1/2" teed off to each fixture. Good luck.
 
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Old 03-12-06, 06:37 PM
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Code

Based on your water supply fixture units, developed pipe length, elevation, a presumed static pressure of anywhere between 40psi and 60psi and no adjustments for pressure reducers/specialty equipment/etc...., The International Residential Code requires a minimum of 1" main distribution pipe for your home with each bath group requiring a 3/4" pipe branch with 1/2" individual supplies.

The kitchen group can have a 1/2" branch and supplies.

Your code may vary.

But for IRC, that's the minimum sizes you can use and be compliant.
 
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Old 03-12-06, 07:15 PM
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fiscally responsible / environmentally conscious

The disadvantage of larger diameter pipe is heat loss - from hot water to the enviroment or from the environment to cold water.
Also water is allowed to run longer waiting for it to warm up or cool down which results in waste.

For these reasons, oversizing is not what I recommend.
 
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Old 03-13-06, 04:31 AM
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Unfortunatlely, 1" pipe is not 'oversizing' of the pipe. It is the minimum code compliant size, even in Pennsylvania.

IRC code requires pipes to be insulated to prevent heat loss/heat gain.

1" is all that can be used where the IRC is enforced.

3/4" for distribution lines given this gentleman's circumstances is too small and a code violation.
 
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Old 03-13-06, 05:12 AM
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Bottom line is to check LOCAL codes. International codes are a guideline and most areas have their own codes that must be adhered to. Northwest Ohio had 1" minimum supply line to house, North Central Florida was 3/4", and where I am in Arkansas is 3/4". I have also never seen a State where it was code to insulate water lines. DIY is a worldwide website and answers to questions are generic in nature. Once again, check local codes.
 
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Old 03-13-06, 05:45 AM
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related question

I have an old house in the city. It is a top/down duplex, 2500 square feet, two hot water heaters. My main supply into the house is flexible 3/4" copper to the meter, one line. The meter has a tag that reports it is .58". Most everything is old galvinized, with 3/4" main lines and 1/2" branches.

Unsurprisingly I don't have awesome water pressure, and there is some conflict with the tenant. The situation isn't horrible, but simultaneous showers aren't so great. The best solution is to run a new, larger line to the street, 1-1/4" maybe. I'm guessing that is going to be a $4-7K fix, and it isn't worth it to me now.

So, my question is, will I gain much by running new pipe from the meter to the hot water tanks. I read that there can be some advantage to going to 1" pipe from a 3/4" service, and also I would be replacing old galvinized with copper. The hot water heaters are about 25' from the meter, and they are the first branches off of the main line. Also, there is an old gate valve after the meter, and I thought that getting rid of this might help. As a second step I would upgrade all of the hot water pipe with copper.

Is this worth my energy? Any other suggestions?
 
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Old 03-13-06, 06:28 AM
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Replacing the galvanized with copper will solve a lot of the problem. I have seen 3/4" galvanized that you could not get a pencil through. I would also replace the gate valve with a ball valve. You are on the right track. Good luck.
 
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Old 03-13-06, 09:18 AM
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Originally Posted by BuffaloDIY
Will I gain much by running new pipe from the meter to the hot water tanks.
This is the last step since it is already copper.


> I read that there can be some advantage to going to 1" pipe from a 3/4" service

This is true. But no doubt the galvanized pipe is corroded.


> The hot water heaters are about 25' from the meter,

That is not far.


> and they are the first branches off of the main line.

Good. All should be 3/4" at this point.

3/4 is plenty for simultaneous showers off separate water heaters.

> there is an old gate valve after the meter,
> and I thought that getting rid of this might help.

Definitely a full-port ball valve will remove a major flow impediment.


> As a second step I would upgrade all of the hot water pipe with copper.
> Is this worth my energy?

Yes. Fix all the indoor plumbing first.
I doubt that the line to the meter needs upgraded.
 

Last edited by bolide; 03-13-06 at 02:41 PM.
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Old 03-13-06, 11:31 AM
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Code in Pennsylvania, Florida, Ohio and Arkansas is identical. And yes, do check them. Local codes will only require the the pipe size to be larger.

1" minimum is required for 9.7 water supply fixture units for distribution lines under International Residential Code. The energy provisions of the same code requires that pipes be insulated.
 
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Old 03-13-06, 11:41 AM
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I will not argue with Manhattan42 in the Forums but I worked in Florida for 11 years and never insulated any water lines and ran 3/4" supplies from the city mains. I also have 3/4 at my current home and the water division ran my line from the main to the meter in 3/4" and it continues to the house in the same size. Guess my area didn't read the codes nor Florida either. I did the work and got the inspections and I know what I did.
 
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Old 03-13-06, 12:58 PM
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Insulated or not, the hot water pipes cool off.
When you go to shave or shower or whatever in the morning, it takes a lot more time, energy, and water to bring a 3/4" copper tube up to temperature than it does for a 1/2" cpvc tube.

On a long run of 3/4" copper, it can take two minutes or longer versus under one minute with 1/2".

Insulation has several benefits -- but so does right-size tubing.
Smaller is better provided that it is big enough.

As for what is in the ground, it should not be too large either.
You want some significant water velocity to keep the chlorine concentration up and to flush through anything that might otherwise settle out and build up.
 
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Old 03-13-06, 01:58 PM
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One clarification, the water meter is inside the house at the basement wall, where the pipe comes into the house.

There is also an old valve right before the meter, where it comes through wall of the basement. Maybe I'll replace this with a ball valve too. Am I allowed to turn the service off from the street to do this work, or do I need some kind of permit? To clarify I mean, for my home, the underground valve that is accessed under a plate that says 'water' on it.
 
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Old 03-13-06, 02:07 PM
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having lived in a 100 year old house in milwaukee, wi [where we do not have hard water problems] i replaced some galvanized with copper. you can barely see daylight through the galvanized; pinhole lumen. flow problems will be about 1000 times more likely to be due to cruddy galvanized than to the difference between 1/2 and 3/4 inch copper or cpvc supply lines. just cut through a water pressurized 1/2 inch cpvc supply line and see how much water pours out in 30 seconds and how far it sprays. don't ask me how i know.
 
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Old 03-13-06, 02:18 PM
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Some Home Centers sell water shut-off tools. Depends on how deep the valve is. The tools I have seen are only 3' long and if your frreze level is lower, the tool won't be long enough. Another problem is that the City usually owns these shut-offs so if you break it, you pay to get it fixed. Most water companies will usually shut off your water by appointment. Just be ready when they come.
 
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Old 03-13-06, 02:19 PM
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>cut through a water pressurized 1/2 inch cpvc supply line and see
> how much water pours out in 30 seconds and how far it sprays.

Probably shoots 20' at 20 gpm horizontally.
So I could imagine 10 gallons pretty easily.

Could be double this if you are at 80 psi.


The catch here is that you are going to 0 pressure at the far end on the entire 1/2" diameter.
A tub spout is like this, but a shower is not.
 
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Old 03-13-06, 02:24 PM
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Originally Posted by manhattan42
... under International Residential Code. The energy provisions of the same code requires that pipes be insulated.
For benefit of those of us who haven't seen it yet, could you cite the article of the International Residential Code (or International Energy Conservation Code) that requires insulating waterlines?
 
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Old 03-13-06, 02:28 PM
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Originally Posted by majakdragon
The tools I have seen are only 3' long and if your freeze level is lower, the tool won't be long enough.
Doesn't your arm fit down the hole?
 
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Old 03-13-06, 02:39 PM
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Bolide,
yes my arm does, barely, but the cross handle on top doesn't.
 
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Old 03-13-06, 02:51 PM
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retroactivity

Originally Posted by manhattan42
3/4" for distribution lines given this gentleman's circumstances is too small and a code violation.
Sounds pretty pointless given that the service line is only 3/4".

I would like to see the table if you can post it.
 

Last edited by bolide; 03-13-06 at 09:39 PM.
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Old 03-13-06, 08:39 PM
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It's not existing anymore; you're replacing it. I've never run anything smaller than 1" into a house. And I don't understand what the concern is. The material cost is negligible between 1" and ", especially if you divide it by the expected number of years that it'll be in service - very likely 50 years or more. It's not any harder to run 1" instead of ". What does it amount to, an extra hundred bucks?

Running " will probably work fine, but what if you want to add a half-bath down the road? Why install the bare minimum when it's so little trouble not to?
 
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Old 03-13-06, 09:28 PM
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Originally Posted by steve_gro
It's not existing anymore; you're replacing it.
I'm sorry, I was thinking the service line.


> I've never run anything smaller than 1" into a house.
Neither have I. But others have. And 3/4" service is the existing size in this case.


> And I don't understand what the concern is.
> The material cost is negligible between 1" and ¾"
> especially if you divide it by the expected number of years that it'll be in service -
> very likely 50 years or more.

I hope they have fire sprinklers and he needs 1.5" before then.


> Running ¾" will probably work fine
> but what if you want to add a half-bath down the road?

Another toilet and sink? I doubt he'll dig up his yard for that.
Those use only 3/8" supply lines anyway. No sense in running a 1" line for that.


> Why install the bare minimum when it's so little trouble not to?

Because it saves time, energy, and water - which achieves the goal of the Code.
 

Last edited by bolide; 03-13-06 at 09:42 PM.
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Old 03-13-06, 09:33 PM
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Numerous opinions all throughout this thread. Starting at the top, the majority of your pressure problems will disappear when doing the changeout from galvanized to copper. You must though check the ports of all the existing faucets and valves to make sure build up is not evident in the years that galvanized leached sediment/buildup into them. Very common and it can restrict flow lower than most ports have in shower valves, isolation valves and the like. (3/8") You definitely need to know what the incoming pressure is starting at a cold outside faucet. Run the faucet 30 seconds to remove any thermal expansion. It should reveal what your water pressure is. If you do not have a PRV on your main line then you will have to gauge the pressure at different times to know if you need protection from high water pressure. Everything in your home is engineered for 60 pounds and anything over 80 requires protection in most areas. This is numero uno top priority.

Second, local jurisdiction of state/local codes can and will be enforced/supercede over IRC/UPC/IPC. The local authority has the right to refuse permits/inspections/final occupancy permits if they so wish. Nothing written in code covering the vast country can be enforced without the local authority first approving/denying it. That is why codes vary/differ from state to state. You can enforce code in one state and it will be relaxed in another, BUT, one particular city in a non-abiding state might enforce a certain "implied" code and there is nothing you can do about it.

So when plumbing discussions start heading toward bookworm knowledge of IRC/IPC/UPC it is generalizing and trying to paint all plumbing schematics with one broad brush. As Dr. Phil states, "That dog won't hunt" It does not apply to all. Residential plumbing, and if you ask any plumber that has walked numerous paths in this profession will tell you that residential plumbing is the simplest form of plumbing there is. Almost novice in some respects. Get into major industrial/commercial applications where you are dealing with 100 to 900 fixture units and then you start addressing plumbing in an engineer's way of thinking. Not to say that residential doesn't have implied knowledge, you are just dealing with plumbings most simplistic form of it.

The thread starter needs to find out what is code for incoming service line size, more than likely the code states undiminished in and out of the water heater from the building wall, then a reduction down to the last 2 or 3 fixtures on 1/2". I don't know if 3/4" or 1" is the norm in your area but a simple call will let you know. You are going to make tremendous gains by removing the galvanized so anything you do is an improvement on all fronts. Doing it right protects you for numerous reasons; codes are designed to provide usage of plumbing fixtures without error/distortion. Resale value, correct pressures to numerous fixtures when used in conjunction with each other.

A great deal of homes have modified plumbing systems due to the lack of enforcement of codes. This follows the logic of "you are the king of your kingdom" rule and most do as they may. It isn't always right, different piping systems are used and sometimes it isn't up to local codes. A great deal of DIY work I have seen is "remove an apple, put an apple back" thinking and this isn't always correct. Codes change over time and with good reason. We do not always agree with them but you cannot interpret the code to your benefit and ignore what is required. You can but in a resale/insurance claim/new house build you will be shut down and failed for doing so. :nfunny:
 
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Old 03-14-06, 11:24 PM
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Yet another good post by Dunbar.
 
 

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