# Question about water pressure in relation to valve and feeder pipe diameters...

Edwin Pawlowski wrote:

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Oh my! So you really weren't just trying to be a wise ass in your reponse to my original post after all! You really do believe what you so clearly misrepresent here as having been suggested!

Ya think?
Ken
"The emperor has no clothes..." -Hans Christian Andersen
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wrote:

You better go back to the books then. The pressure at the output end (the end that we are concerned with) of a flowing circuit can be increased by a larger diameter pipe.
Whether hydraulic or electrical the conduit can restrict flow by creating pressure drops in a active circuit. The OP will not see this benefit in pressure but that does not mean it doesn't exist.
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OK then, what are the number? If you have 100 psi input on a 1/2" pipe that is 10 feet long, what is the pressure at the output?
Then you add 10 feet of 3/4" pipe what will the pressure be at the end.
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wrote:

In your above situation it will be 99.999 psi but it will be lower than 100. If you were to decrease the pipe size it would be even lower. It will not be "NEVER LOWER" as you stated earlier.
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snipped-for-privacy@mucks.net wrote:

Hi, Simply you can't say that. Law of Physics deals with several parameters. For one, if incoming rate of water flow is constant, bigger pipe lowers pressure. It all depends on the situation, rate of flow, intial pressure at the inlet, rate of flow at the outlet, even ambient temperature, etc. all matters. I think you better go back to book as well. Remember Boyle & Charles law?
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No meanings are twisted. Facts are facts. Probably best that you kill file me as I'm not going away. But, if you want to join my fan club, for a \$10 cash payment you get an autographed 5 x 7 color photo of me with my plumbing equipment and pressure gauge.
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wrote:

Yes facts are facts.............
"This Edwin Pawlowski guy is bent on twisting the meaning of what you are saying" " he evidently plays to make himself look 'tall'"
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Can't come up with a disparaging comment of your own so you have to copy another's? Welcome to my fan club. As soon as I receive the \$10 payment, the autographed color photo and membership card will be on their way.
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Guys, guys, guys, why don't we stick to a topic we all know something about, like 'lektricity?
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No dumb questions, just dumb answers.

Larry Wasserman - Baltimore, Maryland - snipped-for-privacy@charm.net
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Ken Moiarty wrote:

It's fun to sit back and watch the new found so called experts argue with people who are the real experts on the subject.
Ed, your not missing anything and your not crazy, some people are just a little thick and it takes longer. Good luck.
kenny b
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No it's not fun to sit back and watch a so called professional make a donkey's ass of himself; transparently pretending to set "non-experts" straight by resorting to arguing against things of an obvious ignorant nature that simply no one suggested whatsoever in the first place.

<chuckle>
My apologies to Larry Wasserman (and everyone else)... I'll let it go now.
BTW, thanks again to all who were courteous enough to accomodate my persistence in my quest for a more complete understanding of facts presented here and elsewhere. I learned what I came here for and then some.
Ken
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This thread keeps getting harder for me to believe! But a tentative picture is beginning to form in my mind that there's some kind of "culture" gap at play between myself and you guys here. If I was rude to anyone, I apologize since I'm beginning to see I may have put a wrong construction on some of the remarks made here. Edwin, you're not American are you? With that smart-ass remark you initially made I had assumed you were (which goes to perceived connotation, believe it or not). I see I really should have not cross-posted to so many groups, otherwise I could have better anticipated what part of the world someone was responding from (e.g. the U.K. in free.uk.trade.plumbing, dah!). Yet it may not just be connotations that are getting misinterpreted here. It must be technical things too. If it's not that then it's either, you guys are all crazy, or (even less likely) I am crazy; scenarios both of which seem to me at this time to be less than highly probable.
"Edwin Pawlowski" wrote...

If you want to put it that way, nor will 'moving into a bigger house increase my income'! I didn't quite mean it the way you have apparently understood me to be speaking. I don't know exactly what psi my street's water main is at. But I do know the pressure in it far exceeds that which reaches my plumbing fixtures. By the same token, I also know that all the 1/2" copper pipes that feed these fixtures are connected to larger diameter (3/4") intermediate pipes ("pipes" in plural as I'm referring to both the hot and cold, respectively) which are at a higher psi, being that it is *less decreased* removed from in the street than is the psi in the smaller diameter 1/2" pipes.
Now I will stop here, and wait for feedback as to just this little bit, before I continue to to finish trying to communicate myself to you on this as least ambiguously as I can manage.

I never implied I was intending to "put in a section" of larger pipe. (The statement in my original post, "if properly done", was meant to assure the knowledgeable reader of my awareness here such as to preclude any such unnecessary confusion.)

Everyone around these parts expects that the pressure at the street is going to be a lot higher than the pressure in the house is permitted to be. I've never heard of both being the same. Certainly no place where I've lived (in Canada, of course) have these been the same. What is it that makes one so automatically presume that mine would be? Or that in presuming that these are the same in my case, that I must therefore necessarily be to oblivious to the obvious futility of any effort to get more pressure than is there to tap into?

It's not going to be 110 psi at my shower since it has to go through reductions in pipe diameter. Herein lies the rub: The less reduction in pipe diameter after the main supply line, the greater (i.e. closer to the original 110 psi) the pressure. Hence my rationale for replacing the 1/2" diameter shower feeding runs (that currently branch from the central 3/4" lines they are tied into), with 3/4" runs instead.
Ken
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You've cross posted to many groups - This reply is from pdaxs.services.plumbing.
I am not sure whether you are wanting a debate or an answer to a question. Either that or you are hell bent to change your supply to 3/4". If the latter is your intent then why come ask anything, just do what you want. You certainly don't need our permission. If it's the former then I am going to give you your answer, but I've been plumbing way too long to debate anyone about anything.
There are two different characteristics that affect the perceived amount of water flow from a faucet. 1. Pressure 2. Volume
Plumbers don't use those terms interchangeably. Upsizing your lines will not increase your pressure. It will increase your volume.....BUT..... ONLY if you change the valve to something that was designed to accept the larger supply lines. The industry standard (in the states) is 1/2". It works just fine on every valve I've installed for thirty years. I thought I read in one of the previous posts where someone brought up your valve. That's the key. If you've tried changing showerheads and/or removing water savers then I'd recommend that you go out and buy yourself a brand new Moen pressure balancing valve and install it.
I thought someone else suggested adjusting your PRV (pressure reducing valve) I have no idea if you have one or not, but if you don't have a history of problems and now you do, I'd look real hard at that valve if you have one. The "moving parts" of any system are always the weak link. Pipe is not a "moving part". If this problem just popped up, look at the "moving parts" first.
Bob Wheatley
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Bob Wheatley wrote:

Increased volume {like able to fill the bathtub up quicker, for example, is this right?} is one thing I definitely want out of all this. But since I've come to understand (after reading Paul's excellent post) that I can't get any *significant* pressure increase as a result of upsizing my lines, I couldn't help but anticipate what you're saying here about the valve having to be one that 's designed to accept the larger supply lines for these larger supply lines to be able to deliver on that.

Just the one that reduces/regulates the pressure for the entire household.

Thanks for this helpful info, Bob.
Ken
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and thankyou God for plumbers, Amen.
kenny b
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And that would be fine if it wasn't for the fact that (in Canada, at least), unless one's a general contractor, a good plumber can be hard to find.
Ken
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Ken wrote:

There's an old retired fellow up in the Falls area (american side), I here he works for "lap dances at mints".
kenny b
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Ken wrote:

Ken wrote:

There's an old retired fellow up in the Falls area (american side), I hear he works for "lap dances" at mints.
kenny b
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Yes, Paul's post was factual. But he's not a plumber. A plumber knows that it is unlikely that you have a 100' of 1/2" pipe supplying a tub valve or any other kind of valve. Making his 3 pound pressure drop a mathematical improbability. A typical house will have 3/4" or 1" coming from the meter or supply source and enter the house in those sizes and not reduce until the last 2 or 3 fixtures. Because those fixtures are typically a bathroom there will "generally" be 3/4" within 20' to 30' of the farthest bathroom in a typical house. The point being here that increasing the pipe size would result in possibly a 1 pound pressure drop increase or less. Probably less. Whatever actual flow rate is gained would not be humanly detectable. Because the ports in a typical valve are generally only between 1/8" to 1/4" to allow the water to flow through, you can upsize until you turn green and the weakest link will always be the valve. If you have good pressure everywhere else in the house then you need to take apart the offending valve and make sure it has no obstructions. Re-piping is a waste of time, money, and effort unless you know the piping system is obstructed with some sort of build up.

You may want to have a professional look at this. It would be my number 1 suspect.
Bob Wheatley
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