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

Page 4 of 5  


If flushing the toilet is the problem, an obvious solution would be to partially close the valve to the toilet so it fills slower.
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
and thankyou God for plumbers, Amen.
kenny b
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@adelphia.net wrote:

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ken wrote:

Canada huh!
There's an old retired fellow up in the Falls area (american side), I here he works for "lap dances at mints".
kenny b
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ken wrote:

Ken wrote:

Canada huh!
There's an old retired fellow up in the Falls area (american side), I hear he works for "lap dances" at mints.
kenny b
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Maybe that's the reason why he was able to see the problem I was having integrating what I had read (about pipe diameter affecting pressure) with what I was merely "being told" in black-and-white terms as being otherwise (without explanation or discussion). The plumbers were completely silent in response to my implied requests for help in reconciling what they were telling me, with what I had read and recalled for them, such as, "The plumber and the plumbing designer rely on the internal diameter of the water delivery pipes to control water pressure" (Bob Vila). By giving me the raw, not paternalistically oversimplified, theoretical information [i.e not merely what the 'doctors' judged to be all that the little 'patient' need concern himself with] Paul was able to help me make logical sense of what I was "being told" with respect with what I had previously read.

I think Paul's explanation made this quite apparent.

It was to clarify specifically just this question that I posted my query here in the first place.

Was it not you who said that larger pipes will nonetheless deliver greater volume (providing the corresponding capacity valves, etc.)?

Yes, that is the industry standard here in Canada too (for houses). But I've long noticed in commercial buildings (like the hospital where I work) they have 1" pipes leading directly to things like toilets. These toilets (without a tank) flush prodigious amounts of water in just a second or two. Unless there is more to these systems than meets my eye, it would appear to me that larger diameter pipes do allow more water to get through quicker.

Being strapped with paying on a huge mortgage (huge only because entry level property values are staggeringly high here in Vancouver) while earning only a very modest income, I just can't afford to hire a reputable plumber for anything that isn't an emergency. So I have little choice but to just try my best at being as handy and knowledgeable a 'jack-of-all-trades' as I can be in responding to my house's needs.
Ken
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
There's a lot of misinformation and incomplete information in this thread. Let's bring some citations and facts to the game. You wanted details and facts, here you go.
At least part of the mess here is due to confusing static pressure and dynamic pressure. In this context, static pressure is the pressure at a specified point in the system when flow is zero. Dynamic pressure is pressure at a specified point in the system when water is flowing at some non-zero rate.
What you asked about is the dynamic pressure at the showerhead when the water is flowing at whatever rate it flows when you have the shower on. The greater the dynamic pressure at that point, the more forceful the shower stream will seem, for a given showerhead. Yes, as many posters have pointed out, different showerheads will feel better or worse all else being the same, but for a given showerhead, the higher the dynamic pressure at the showerhead, the more forceful feel the water streams will have.
So first a word about static pressure. The static pressure at the shower head is determined by the static pressure at the point your water pipe enters your house, minus 0.433 lbs for every foot of elevation difference between the entry point and the shower head, assuming your showerhead is higher than the entry point and you don't have a pressure regulator valve. So if the static pressure at the entry point is 50 lbs, and your showerhead is 10 feet higher than the entry point, the static pressure at the showerhead will be 45.67 lbs.
Note that pipe size (within reason), number of turns, fittings, etc., does not enter into this. So when a previous poster says pipe size doesn't affect pressure, they are talking about static pressure (or they are wrong, see below).
For a good explanation of static pressure, see:
http://www.nationaldriller.com/CDA/Archives/e125cc2ce4197010VgnVCM100000f932a8c0____
On to dynamic pressure. When water flows through a pipe, a pressure drop occurs along the pipe due to the energy that is required to overcome the friction between the pipe and the flowing water. Pressure drop in a pipe is affected by flow rate, the viscosity of the liquid, the diameter of the pipe, and how smooth the pipe interior is (corrosion and deposits increase pressure drop).
Fittings such as els, tees, shutoffs, etc., also cause a pressure drop, and for the same reason. Pressure drop for fittings is often expressed as the length of equal diameter pipe that would cause the same pressure drop at the same flow rate.
For an example, a 1/2 inch copper el has a pressure drop equivilent to 2 inches of 1/2 copper pipe. A 3/4 copper el has a pressure drop equivilent to 3 inches of 3/4 copper pipe.
Pressure drop is usually expressed as lbs per 100 feet of pipe at a given flow rate. For an example, water flowing at 2 gpm through 1/2 copper pipe will have a pressure drop of 2.6 lbs per hundred feet. For 3/4 copper pipe under the same 2.0 gpm flow, the pressure drop is 0.5 lbs per hundred feet.
For a good explanation of pressure drop and tables for pipe and fittings see:
http://www.nationaldriller.com/CDA/Archives/0dbf5d7935197010VgnVCM100000f932a8c0____
What does all this mean for your shower?
Let assume the pressure at the entry point to your house is 50lbs. Lets assume you have 4 elbows and 100 feet of total pipe length (not counting the elbows) between the entry and your showerhead, and that the showerhead is 10 feet higher than the entry point. Let's also assume copper pipe and a flow rate of 2 gpm. What will be the dynamic pressure at the showerhead with both 1/2 inch and 3/4 inch pipe?
Dynamic pressure at showerhead equals static pressure at entry, minus static pressure drop due to change in elevation, minus dynamic pressure drop in pipe, minus dynamic pressure drop in fittings.
For 1/2 inch this is:
50 - (.433 x 10) - 2.6 - (((4 x 2) / 1200) x 2.6) = 43.0527lbs
For 3/4 inch this is:
50 - (.433 x 10) - 0.5 - (((4 x 3) / 1200) x 0.5) = 45.165
All the figures come from the cited references.
The complicated term is the number of ells times the equivilent length of pipe in inches divided by the number of inches in 100 feet, times the pressure drop of pipe per 100 feet.
So for the above example, the dynamic pressure will be a little over two lbs greater for 3/4 pipe compared to 1/2 pipe. Will you notice it standing in the shower? I doubt it.
You will notice that the pressure drop due to elevation change is the major factor, followed by the dynamic drop of the 100 feet of pipe. The elbows contribute only a tiny amount.
Sticking a valve in the pipe will add a dynamic pressure drop term to the calculation. The magnitude of the term will depend on the valve and the flow rate but it will be the same for the two cases, so you will still be better off (albeit only a tiny bit) with 3/4 pipe.
For completeness I will mention one complicating factor. The above calculations assume the same flow rate in both cases. However, in practice this won't quite be true, because the dynamic pressure is higher in the 3/4 case. This will mean the flow rate will be slightly higher, which will increase all the pressure drops slightly. The net affect is that the difference in practice will be even less than shown above.
I hope this helps clear up some of the confusion.
Paul Franklin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

http://www.nationaldriller.com/CDA/Archives/e125cc2ce4197010VgnVCM100000f932a8c0____
http://www.nationaldriller.com/CDA/Archives/0dbf5d7935197010VgnVCM100000f932a8c0____
that some posters were referring to static pressure and others to dynamic pressure without stating which.
I agree with the conclusion that increasing the pipe size is very unlikely to satisfactorily solve the problem. The 1/2 inch pipe is adequate for the service and is pretty much standard in the plumbing systems I have come in contact with. I suspect low source pressure, a faulty reducing valve, a localized restriction such as a clogged screen, obstruction in the pipe, or obstruction in the valve. It is also possible that the pathway has generalized obstruction caused by deposits in the piping. If there is another restriction, then increasing the pipe size will theoretically and actually increase the water flow, but it is unlikely to be any significant amount of increase.
Don Young
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Paul Franklin wrote:

You've hit the nail right on the head! A lot of "incomplete information" and/or incomplete communication (which I'll admit to being a part of, as well).

http://www.nationaldriller.com/CDA/Archives/e125cc2ce4197010VgnVCM100000f932a8c0____
http://www.nationaldriller.com/CDA/Archives/0dbf5d7935197010VgnVCM100000f932a8c0____
That slight of a pressure difference, eh? Now it's all beginning to make sense to me.

Yes, yes. I see it now.

This has most certainly done so for me. My questions are now finally satisified. I thank you very much, Paul.
Ken
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes, I am in the US. As for my wise ass comments, you asked for opinions and I offered one. If you don't want to hear what I have to say, don't ask. No, I'm not a bully at hte keyboard, this is wha I am in real life.

OK, this means there is either a PRV (pressure reducing valve) or s ome sort of restriction. Unless you check actual pressure with a gauge, you can't be 100% sure of anything in finding hte problem.
By the same token, I also know that all the

For that to occur, the flow rate has to be very high. 1/2" is a common size feed in residential use and at the fixture 3/8" or 1/4" is common. The 1/2" feeding them is very adequate.

In my last three houses, and in the two bildings I mantain, the inside pressure is the same as the street, except for locations wehre we've intellionally reduced it. Since on of the building sis our prductin facility, we have a fewgausges so we can monitor this. We also have a self contained recirculation system that we maintain at 80 psi with pumps.

No, this is where you are getting confused.

It still comes back to flow. Increasing the pipe diameter is not going to increase the pressure if the pipes are restricted in any way or if the flow is not controlled. Take a look at your garden hose. If you have an open end, turn the water on full flow, the water may come out at about 3 feet from the end of the hose. Put a nozzle on the end. Now, you have the same pressure in the hose as before, but with a restriction in the tip, you can shoot out a stream for maybe 20 feet. Note that the open hose will, though, fill a bucket much faster.
This takes us full circle back to my original suggestion that you may get more satisfaction in your shower by changing the head, not the pipes feeding it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ken Moiarty wrote:

I think you posted to argue, not to gather information. Simple answer to your original question, increasing pipe diameter as you stated won't make any difference. May make things worse. I thought water saver shower head was a good idea. I live in Calgary in a house with 4 bath rooms. All my plumbing is done to save water and our water is on meter. Remember water is becoming scarce and we have to do everything to conserve it. My son is in water conservation and waste water recycling. According to him, the outlook is pretty grim for good water supply in the coming years. Sounds like you have this idea of your own and trying to justify it to try. Then just go ahead and try and come back here to report the result.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My apologies. I replied to your message last night from my work computer, through Google Groups (since it doesn't have direct newsgroup access), and forgot that my display name is slightly different there ("Ken" instead of "Ken Moiarty"). So I'll paste and resubmit my reply to you below.
--

Mike Grooms wrote:
> Ken,
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've never lived in a house with such a problem, and I've seen some pretty corroded galvanized pipes. It would take a significant constriction in the cold line to make this a problem if you have reasonable supply pressure.
You really need to be looking at your static water pressure and make sure all valves in the supply are open fully.
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob F wrote:

Wow! This is like a paradigm shift (so to speak) for me. Got any suggestions as to what to search for in order to learn more about this? Apparently production housing contractors in my part of the country are either all helplessly second rate, or are colluding to 'pull the wool' over consumers' eyes in this matter. (Based on my long-held displeasure due to a lack of attention to quality _in general_ from these "slap-n-tack" outfits, I'm personally inclined to believe the latter.)
Ken
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote in message

You sound skeptical if my claim. What parts of the country have you lived, if I may ask? Have you lived in custom built houses or production built (or both)? I have no doubt that you have never experienced this while showering, or even while washing your hands for that matter. After all, just because my experience has not been the same is not sufficient cause to doubt what you report as having been your experience.
Ken
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If you increase the pipe size you can increase the flow rate / pressure. I run 3/4 right up to every shower. I especially do it on well pressure.
If you are on city water with good pressure then you must have an obstruction.
I would need to know how many psi we have to size the pipe to get the right gpm at your pressure.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.