Do PEX fittings reduce water flow? (PEX VS Copper)

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curious1

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PEX fittings go INSIDE the pipe. They are therefore smaller in diameter)

A 3/4 PEX fitting is equaly wide as a 1/2 copper fitting - this reduces the water flow.

Does that mean that when I replace 1/2 in copper (example for a shower) I should use 3/4 PEX?

(On the other hand PEX uses almost no elbows and no 90 degree turns etc. - this factor increases the water flow)-



(P.S. NYC has ridiculous rule not allowing any PEX to be used in fresh water (officially because of rats but that is false since (I think) it is allowed in radiant pipes which are also prone to rats -) This is probably because of plumbers union (who want to rob consumers by forcing the use of copper which is 10x more work and needs special skills). Because of all these crazy rules - it cost a few hundred dollars for a tiny plumbing job . Any comment on this?
 
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WJcandee

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NYC doesn't allow braided hoses for toilet installation either, although people do it all the time.

The reason for requiring hardlines most likely has to do with the fact that NYC has a very high concentration of multifamily housing, and water dumped in one place in a new or old multifamily building is going to do a lot fo damage before it pours out in the lobby. The plumbing code here is strict in large part because the consequences of a leak will be more likely to affect a lot of people than elsewhere. For the same reason, the use of non-plumbers to do plumbing is smacked down hard here -- no super in any building who values his livelihood is going to permit it, and the unions are also super-vigilent about the issue, much more so than in many places.
 

hj

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Radiant lines are usually buried in the floors or walls making it difficult for rodents to damage them, and in many cases, even if they did, the water damage would be much less. The unions have many more "make work" requirements in the code, so don't just single out PEX.
 

curious1

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NYC doesn't allow braided hoses for toilet installation either, although people do it all the time.

The reason for requiring hardlines most likely has to do with the fact that NYC has a very high concentration of multifamily housing, and water dumped in one place in a new or old multifamily building is going to do a lot fo damage before it pours out in the lobby. The plumbing code here is strict in large part because the consequences of a leak will be more likely to affect a lot of people than elsewhere. For the same reason, the use of non-plumbers to do plumbing is smacked down hard here -- no super in any building who values his livelihood is going to permit it, and the unions are also super-vigilent about the issue, much more so than in many places.



Yes a cramped City does need more strict rules even for water piping. But it goes out of hand. Outside of NYC you could have an experienced handyman plumber run a pex pipe for 200 dollars - In NYC you need to call a licensed plumber and often file which could cost 2-3 thousand for the same job.
 

curious1

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Radiant lines are usually buried in the floors or walls making it difficult for rodents to damage them, and in many cases, even if they did, the water damage would be much less. The unions have many more "make work" requirements in the code, so don't just single out PEX.

What about the pex vs copper question?
 

curious1

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Pex fittings go INSIDE the pipe. They are therefore smaller in diameter)

A 3/4 pex fitting is equaly wide as a 1/2 copper fitting - this reduces the water flow.

Does that mean that when I replace 1/2 in copper (example for a shower) I should use 3/4 pex?

(On the other hand pex uses almost no elbows and no 90 degree turns etc. - this factor increases the water flow)-



(P.S. NYC has ridiculous rule not allowing any pex to be used in fresh water (officially because of rats but that is false since (I think) it is allowed in radiant pipes which are also prone to rats -) This is probably because of plumbers union (who want to rob consumers by forcing the use of copper which is 10x more work and needs special skills). Because of all these crazy rules - it cost a few hundred dollars for a tiny plumbing job . Any comment on this?

Thanks for all your responses ( all got likes) what about the main question - PEX VS Copper flow restriction?
 

Reach4

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Reply #3 was clear; if you want no more restriction with PEX than you have with 1/2 inch copper, go up to 3/4 pex.

However 1/2 inch PEX for the hot line would let hot water get to the shower quicker.

Uponer /Wirsbo PEX fittings are larger than crimp PEX fittings.

What is not clear is if you have a question. Nobody is arguing your points.
 
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Jadnashua

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To a point, a short distance of restriction does not reduce flow as much as a longer section of smaller diameter piping because the water can speed up through a small section. It's a function of friction. It will have no effect on static pressure, but enough friction will affect the flow volume. Keep in mind that the area of the opening uses the square of the radius, so even a small difference makes a much bigger change - IOW, it is not linear, so every little bit helps. Pex-A using expansion fittings give you a little more ID.
 

asmad

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I also have a project in which I was going to transition from 1/2" copper to PEX. But the point where I will transition is very close to the copper supply. From the copper/PEX transition, I will put a tee on - end going straight up to shower valve, the other going over about 2-3 feet for a tub faucet. So given what was said here about long distances vs short distances, am I ok with 1/2" PEX? Sorry, didn't mean to hijack your thread but since we basically have the same question I thought I'd chime in.

BTW, I've wondered the same thing but didn't even think it was an issue until I stumbled on your thread. I'm surprised at the answers you've gotten.
 

curious1

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Reply #3 was clear; if you want no more restriction with PEX than you have with 1/2 inch copper, go up to 3/4 pex.

However 1/2 inch PEX for the hot line would let hot water get to the shower quicker.

Uponer /Wirsbo PEX fittings are larger than crimp PEX fittings.

What is not clear is if you have a question. Nobody is arguing your points.

Thanks.
I also pointed out that pex has much less 90 degree turns - Does that usually fix the slow flow problem? See my comment at the bottom of the thread - I will clarify the question.
 

curious1

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To a point, a short distance of restriction does not reduce flow as much as a longer section of smaller diameter piping because the water can speed up through a small section. It's a function of friction. It will have no effect on static pressure, but enough friction will affect the flow volume. Keep in mind that the area of the opening uses the square of the radius, so even a small difference makes a much bigger change - IOW, it is not linear, so every little bit helps. Pex-A using expansion fittings give you a little more ID.

Thanks. I will check out Pex-A.
 

curious1

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Thanks for the responses I thumbed up everybody. Let me clarify:

Radiant water heat usually uses 3/4 copper. When I use pex (with old radiators) could I also use 3/4 pex? or do I need to use 1" pex which is much more difficult and expensive?

On one hand the small fittings only make up a small portion of the water flow, plus - pex has almost no sharp turns. One the other hand the fittings ARE smaller?

Most previous answers were to go up a size - that is expensive I want to confirm. Some users gave ideas involved using expensive kinds of fittings that have a larger diameter. What about the old standard Crimp?
 

Reach4

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I see you edited your original question to be more about adequate function than academic about which was larger. So it is now a harder question.
 

Jadnashua

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OFten with radiant, instead of going bigger, you make more loops, but it takes some careful calculations to determine which is better. With any radiant loop, though, there is a maximum length you can use that must be adhered to, or you'll have too much friction, and maybe not enough heat at the end of the loop. It's a very careful balancing act. You can't have the flow rate too high. ALso consider that a smaller tube has more surface area per volume than a tube with a larger diameter. This also affects the heat transfer. There are some fairly sophisticated software programs that take al of this into consideration and provide recommendations.
 

curious1

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OFten with radiant, instead of going bigger, you make more loops, but it takes some careful calculations to determine which is better. With any radiant loop, though, there is a maximum length you can use that must be adhered to, or you'll have too much friction, and maybe not enough heat at the end of the loop. It's a very careful balancing act. You can't have the flow rate too high. ALso consider that a smaller tube has more surface area per volume than a tube with a larger diameter. This also affects the heat transfer. There are some fairly sophisticated software programs that take al of this into consideration and provide recommendations.

Yes I had that problem in the past where the water was not moving quick enough and causing the boiler to overheat. Instead of doing over all the piping - I fixed it by adding a second pump right on top of the first. This moved the water quicker. Also I needed to lower the flame size of the boiler. But these are not the standard way of doing things. It also waists electricity for the extra pump and takes more time for the home to heat up due to the lower flame.
 

Terry

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1/2 PEX works fine for a tub or shower.
If you have multiple heads, then you may want to consider 3/4" PEX.

Always; if you have a tub/shower, you will need to run copper to the tub spout and not PEX.
 

Mike Garrod

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Pex/plastic pipe have higher flow rates than copper. However pex fittings ID (inside diameter) is smaller than the pipe of the same size, so it actually does impede water flow. Wirsbo pipe on the other hand is expanded to fit around the fitting which has the same ID as the pipe. Wirsbo is the way to go in my opinion.
 
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