See article at
"... manipulation of pressure is achieved entirely by varying the internal diameters of the pipes."
Ken
Increased volume and velocity of the water _exiting of the shower head_ is what I want (what I "only need" is nobody's concern here). This is not to be confused with velocity of flow in the supply pipe (i.e. the copper pipe in the wall), which by itself has nothing to do with the velocity at which water will exit the shower head. While the _velocity_ of the same or similar quantity of water exiting the shower head may well be increased by a low flow shower head (which I'm simply not interested in here for my own reasons not related to anything being discussed here), there's no logical reason to believe that volume (or quantity of water delivered per second) will increase without an increase in supply pipe pressure. And besides, if somehow a low flow shower head were to somehow result in an increase in volume (quantity of water delivered per second) that would only fly counter to the reason for the existence of "low flow" shower heads, which is, to >decrease< (not increase) water consumption. So either you are so bent on promoting water conservation devices that you'll say anything, however confused, to get others to buy into the sales hype, or you are someone who has succumbed to becoming confused by such hype yourself.
Then tell us your experience. I'd like to know the particulars about it, as opposed to only what you've personally come to conclude 'in lieu of' it, please.
TIA, Ken
Ken,
I noticed everyone and his mother has been giving you advice. This is coming from the plumbing newsgroup.
Increasing the feed pipes to 3/4" won't help. Incidentally, since water is not compressible, the smallest pipe or port in the system affects whatever's after it.
Here's three thoughts..
#1 Is the shower the only place in your house where this low pressure occurs? If this problem exists elsewhere, write back for more advice.
#2 Since the problem isn't a clogged shower head (which was the first thing to check), then, assuming some rust hasn't lodged in the valve body, I'd suspect the balancing valve itself. If you're handy enough, take the valve out and see if that doesn't increase the pressure. If it does, then just get a new valve. BTW, you shouldn't need a balancing valve. Something is awry somewhere. Perhaps you'll end up repiping the main arteries that feed the fixtures.
#3 Don't ask plumbing questions in the "alt.home.repair" group, unless you want a bunch of amateurish, faulty advice.
First do what I've suggested, then write the plumbing group if you need more advice. Sice we're not there to look at things ourselves, it might take a message or two.
Thanks. Finally a response suggesting credibility.
Okay, this appears on the surface to be saying exactly what others before you have been saying. Am I to be sure then that you mean to be saying here that using 3/4" pipe in place of the current 1/2" pipe
*won't* result in less pressure loss (in relation to the main supply line into the house)? If so, maybe you could indulge my curiosity and explain how this can be so in light of the many references that appear to say otherwise (such as the "Bob Villa" reference I quoted, for example)? But somehow I'm inclined to to think you don't mean to be saying this at all, but rather could be somewhat misunderstanding my original post.Thank you!. So a reduction in pipe diameter from, say 3/4" to 1/2" for a travel distance of, say, 4" (the length of my PB valve) and then back again, would definitely limit the pressure at the end to what it would be if the entire line were just 1/2" in diameter to begin with?
No, the pressure is low throughout the house. (Bear in mind, however, that when I say "low", I don't mean abnormally low; just lower than what I've been used to from older dwellings I've lived in prior. I can write back later and give you the actual psi value since my memory is not so numerically precise, but I will tell you now that I recall checking the water pressure at an outside faucet in the past and finding it to be within the lower end of the normal range.)
Okay, I don't have the valve installed yet. When I bought this house there were no pressure balance valves installed whatsoever. Since the time it was built however, local laws have come into effect that require these be installed for each shower in all new (as well as legal rental) dwellings. I have bought an inline pressure-balance valve still waiting for me to install. But it's openings are only standard
1/2", as opposed to the 3/4" piping I have more recently been thinking of installing for a separate and totally distinct reason (i.e. my personal preference for increased overall pressure to shower - think 'President Lyndon Johnson with his 100 PSI shower in the White House...', though not necessarily that extreme )..., thus prompting my original question.This comes to me as a surprise. In every house I've ever lived in prior to, as well as including, this one, people have had to time their showers (or tell others before showering) in order to avoid being scalded or cold-shocked while showering. I remember my Dad turning down the thermostat of a new hot water tank that had just been installed in his house, as a safety precaution to decrease the chance of somebody getting seriously injured while showering in the event that somebody opened or closed a tap somewhere unawares during.
Okay, thanks for your helpful feedback.
Ken
Yes, this is what I'm thinking could be the case. But I would like to find out for more certain.
This shower's on the lower floor.
Yes I've thought of this. But I'm not comfortable with the idea of increasing the pressure for the entire household. If one of my neighbors learned I was doing this during the summer months when water restrictions are in effect (and inexplicably, water pressure for everybody in the neighborhood always seems to be much lower than during the rest of the year), I'm pretty sure I'd soon receive a visitor from the city abruptly ordering me to 'shut er down' due to some bureaucratic bylaw prohibiting such. (Hey, in this city where I now live it's even illegal to use a sump pump, because -silly as it may seem- that is considered to be abuse of public sewer system capacity.)
Ken
"My shower lacks pressure so I want to replace the existing 1/2 inch copper pipe that leads up to it with 3/4 inch copper pipe. Obviously, if done
correctly this will increase the water pressure available at my shower."
The first paragraph of your post is incorrect and untrue. It makes me wonder how you could be so judgemental of everyone's response when you don't have a clue of what your asking yourself.
kenny b
Thank you. Your feelings are noted, kenny bs.
Ken
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.
kenny
Now Kenny, is that the way we plumbers write? You're going to give everyone the impression that we're a little harsh.
Sorry I'm trying to stay away from the 4 letter words that come so easy to us every day, it's the new me.
kenny b
Pressure and volume are different things. Increasing the pipe size will NOT increase the pressure. Can't happen. Won't happen. Put in a 6" pipe and you won't get any more pressure If your feed from the street is corroded, you may get better flow by replacing it, but putting in a section of larger pipe will do nothing.
If you want to increase the pressure, the first step is to find what pressure is at the street. Then you compare that to your house. If they are the same, nothing you do will increase it. If you get a big pressure drop, it may be from a flow restriction on the main to the house. What size and type of pipe is it? If it is an old galvanzied pipe it may be corroded or have buildup inside and giving restriction. This is a different scenario than what you are suggesting. Replacing a section inside will do nothing.
If you want a high pressure shower, move to the town that I work in. We have 110 psi feed.
In the original post increasing the size won't do anything measurable, "Can't happen. Won't happen" I don't think so. In theory and in practice with long runs pressure drops will add up and increasing the pipe diameter will increase the pressure at the output end.
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
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.
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
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.
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:
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:
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) = 43.0527lbsFor 3/4 inch this is:
50 - (.433 x 10) - 0.5 - (((4 x 3) / 1200) x 0.5) = 45.165All 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
Increasing diameter increases flow, not pressure. Pressure is determined by head, or height of fixture relative to height of water source if no pumps are used. Increase pressure by having your town buy a new water tower.
Increasing to 3/4" would be useful for multiple showerhead fixtures.
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
This is a real good and complete explanation of the situation. I had noticed 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
Increasing pipe diameter reduces restriction on the flow. Static pressure remains exactly the same. There will be less pressure drop once the flow is started. But pressure is never increased by larger pipes.
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