Dear Lazyweb, I am having an issue with a series of tubes.

I have crappy water pressure in my shower. However, the sinks in my bathroom and kitchen have no such problem. The sinks have the fury of a geyser, compared to the anemic mist the shower puts out. My high-tech measuring methodology is this: in any of my sinks, I can fill up a pint glass in about 1.7 seconds, with either hot or cold water. However, if I use either the bathtub faucet or the shower (with the shower head removed, so it's just a bare pipe) this takes about 8.2 seconds.

So the water is there, it just ain't making it to the shower. The sink looks like this, and the valve in the shower looks like this:

They appear to both be fed by the same 1/2" flex-tubing. The two screw-valves on either side of the shower valve assembly are turned all the way up.

I had a plumber come out and he said that he could replace the shower valve assembly (which would require turning off the water to the whole building, knocking out the wall, and re-tiling), but that it likely wouldn't make any difference, so I should just live with it. He seems to suspect that all such valves are standardized at a "crappy water pressure" setting, and replacing it would leave me exactly where I am now.

I can't see any markings on the thing in the wall that would let me research what its flow is actually rated to be, so that I could compare it with potential replacements.

Any thoughts?

Update: I took out the flow regulator that was hiding behind the big screw thingy that is 2nd from the right in the right picture above (it's the smaller part pictured to the right, here), and now I get 1.7 second flow from both the tub faucet and the showerhead pipe! Unfortunately my shower head still retards that down to around 4 seconds, so it's time to find a better one of those...

Update 2: I spoke too soon. It seems that taking out the flow regulator increased the flow of cold water but not of hot water, so after taking that out the shower was slightly-warm at best, never hot. So apparently I get to choose between good water pressure and hot water.

The hot water valve on the left doesn't open as far as the cold water valve on the right does (one turn versus two), so maybe that's the problem. But replacing that would definitely require opening up the wall and de-soldering the pipes.

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46 Responses:

  1. wasteddream says:

    How old is the plumbing? And how old is the plumbing to which it attaches further up the line? It's possible your pipes are choked with debris.

    Has the shower ever had good pressure? How about your neighbors, who presumably are equipped with the same fixtures?

    • jwz says:

      Constructed in 1990. Shower has been the same since I moved in in 1997. No idea about the neighbors. But since the sink and the shower are like 3' apart, it seems unlikely that they feed from different sources upstream.

      • wasteddream says:

        Find out about the neighbors' shower. If they have pressure and you don't, then something is clogging your shower between the nozzle and the point where the supply branches from the sink. This happens all the time when an old section of pipe is disturbed and all the tiny bits of corrosion and whatnot break off, flow downsteam, and collect in a smaller area, such as a shower supply line.

        • pallmalls says:

          Even crazier things can get stuck in the lines. A colleague just had to have a plumber remove a hunk of rag from one of the lines in their new house. When plumbing is roughed in, oftentimes the contractors will plug the open ends of the unconnected pipes with rags to keep them from getting other construction debris in them. Of course, if a chunk of cloth gets shoved down too far in a pipe and no one notices...

          • scullin says:

            Yeah, one forum I was reading trying to sort out my own exciting plumbing recommended using bread for those purposes, which I suppose at least dissolves, but seemed kind of gross in its own right.

        • cfs_calif says:

          It could be that gunk has accumulated in the aerator in the shower head itself.

          Take off the shower head and see if you get good flow without it. If you do, the solution is self evident.


          • discogravy says:

            However, if I use either the bathtub faucet or the shower (with the shower head removed, so it's just a bare pipe) this takes about 8.2 seconds.

      • tkil says:

        If there's a way to turn off water to the shower -- and it looks like the two "screwy things" on either side of the valve assembly will let you do that -- then you should be able to pull out the cartridge behind the handle.

        (Ok, it's [obviously] not quite that simple. Assuming you can turn off the water, then this style of one-handled "washerless" cartridges typically can be removed by: 1. pry out set screw hole plug, usually on bottom of handle; 2. use hex wrench to loosen and remove set screw and hence the handle [warning, Moen at least defaults to something insane like 7/64"]; 3. use needle-nose pliers to remove c-clip; 4. use cartridge puller to extract existing cartridge.)

        I had an issue with clogging on a brand new cartridge that I installed into our kitchen faucet; it turns out that crumbly rubber bits (likely from the previous cartridge) had gotten stuck in the innards of the new cartridge. Blasting it with water a few times, and letting the water run out of the cartridge seat, made all the difference in the world.

  2. scullin says:

    Trying not to make a fool of myself with english units, it seems that even without a shower head (which typically does the flow restriction, not just the valve), you're getting a gallon in ~65 seconds, or less that 1gps, which is pretty sad, even by water conservation standards. I don't think your plumber was necessarily top notch.

    I would at least turn off the water and disassemble the valve to make sure there's not sediment or scale clogging it. Replacing the valve innards is relatively straight-forward if they're all scaled up.

    • violentbloom says:

      and of course check to make sure you don't have copper with galvanized steel like here at our house, which fills up the pipe with rust.

      Of course if that was the case, it's likely it would just fall of in you hand too.

      • biggeek says:

        I was about to suggest that. My Brother ended up replacing all of the plumbing in his house because the galvanized steel pipes looked like clogged arteries.

  3. danomite55 says:

    I had this exact problem in an apartment condo I lived in. My roommate's shower was stellar; mine was pathetic. A plumber used a snake up behind the shower head and was able to pull out a bunch of debris, most of which seemed to be sediment and even some small pebbles (!). After he did that, my pressure was nothing short of spectacular. The most annoying thing was that I "just lived with it" for 9 or 10 months, and I was only there for a year and a half.

  4. shmigs says:

    I found to be a helpful forum to pose my plumbing question.

    Unfortunately, I think a username is required to post. Bug Me has a working login if you want to avoid the hassle of a new one.

  5. movingfinger says:

    You may have one or both of two things going on: 1, sediment (mineral precipitates or other debris) accumulating behind the shower head to clog the line; 2, a flow-control (reduction, for water conservation) device.

    There is probably a pressure-equalizing device in your shower line that keeps you from getting scalded when the cold water is turned off elsewhere (what the plumber you had in seems to be referring to) but this does not mean you have to have crappy water pressure in the shower.

    Lone Star Plumbing in San Francisco sorted out a similar problem for us and suggested that we take the shower head off periodically and soak it in white vinegar to reduce the mineral deposits. Water in SF isn't real hard, but apparently there can be some deposition. They removed the flow-reduction thingy. Our shower has been satisfactory since they did these things.

    I've had some pretty dumb (or scamming) plumbers come round. They are not all intelligent and they do not always come up with the right solution.

    • andr00 says:

      I had been having the crappy-pressure problem since some plumbing work a couple months ago and was just about to give up and call the landlord when lo and behold, jwz invokes the lazyweb to solve my problem. It turned out to be some little rocks stuck in the flow limiter. Took that thing out, and it's party time again!

      I am sad that jwz's problem was not so easy to fix. A wimpy shower is a terrible way to end the day/week/month/dev cycle.

  6. lusty says:

    Does the water flow change if you choose all-hot or all-cold? We had a problem with our mixing valve where if we tried to get hot water out of it it barely dripped, but set to cold there was no problem.

    • moonwick says:

      On that note, it'd be worthwhile to know if the same 1.7-sec fill measurement also applies to only hot water from the sink. If hot water at the sink is also slow, the problem would be farther upstream.

  7. genericvox says:

    Coincidentally I have the same problem. If there's quick fix, I'd love to hear it....

    Good luck.

  8. wtfwtf_ok says:

    Is it a low-flow device inside the shower head? Sometimes those can be removed.

  9. heresiarch says:

    latemodel and i have a great plumber if you want a second opinion, based on the various suggestions here. although, did you talk to your DNA plumber? because we liked him too (he hooked up our stove for us).

  10. jlevetin says:

    I once had a shower that provided the best pressure ever. The residents rejoiced, guests were impressed, and life was good. Then, it began to leak and we replaced a two valve model with a new one, similar to yours. The pressure dropped, the skies darkened, and life became more sucky - I blame lawyers.

    You see, the original had 2 valves. New ones have a single complex valve that provides a constant temperature at the expense of pressure. This prevents the old "triple flush of death" - getting scalded when somebody flushes the toilet (or 3 toilets, in the case of a dorm).

    I agree with your plumber that any replacement will probably fail to perform. There's probably some law that makes it a crime to use a non-constant temp model. Again with the lawyers.

    I suggest that your only hope is to find an old, working 2 valve model and a plumber that will install it. Be ready for fluctuating temperature, though.

    But wait, can't they make a constant temp model that provides max pressure? Probably, but it would be expensive. Think about how it probably works. A ratio is set between hot and cold - which determines the temp. The valve then sets the pressure to the lesser of the hot/cold water coming in. Add some C pressure for overhead. Take into account that somebody is probably always flushing a toilet.

    Here's my theory
    2 Valves: pressure-out = pressure-of-hot + pressure-of-cold
    1 Valve: pressure-out = Max(pressure-of-hot,pressure-of-cold) - C

    See the problem? This is also consistent with the provided data. Your sink is a 2 valve system , right? Or doesn't have a constant temperature valve.


    • pozorvlak says:

      Surely it would be 2*min(pressure-of-hot, pressure-of-cold) - C? If you somehow regulate the pressure of the higher to the pressure of the lower, and then mix them, wouldn't the pressures add?

      This would have limited effect on the pressure of the resulting flow unless the two pressures were very different or if C was high.

      • jlevetin says:

        That's a good point and I realized I may have botched the equation.

        I think the ideal "thermostatic shower valve" would follow your equation:

        2*min(pressure-of-hot, pressure-of-cold) - C, with C being very small.

        In my experience we're not even close to the ideal pressure. I think actual device has some arbitrary low pressure it maxes out at, giving this as the equation:

        min(2*min(pressure-of-hot, pressure-of-cold), some-arbitrary-low-pressure)

        Or the first equation is the one, but C is way too large.

      • jlevetin says:


        Seems like there is a difference between a
        "pressure balanced anti-scald valve" and a
        "thermostatic temperature control valve"

        The pressure balanced ones are cheaper and drop the water pressure.

        I'll modify my existing recommendation and suggest a thermostatic temperature control valve.


        "Where flow and volume control are important, a better (and more expensive) choice is a thermostatic valve. Most of these have 3/4-inch inlets that can blast a flood of water through multiple showerheads and will maintain the water temperature within 1 or 2 degrees of the set temperature."

        • I used to not believe in these, having never used one that worked worth a damn, and so it was with some trepidation that I moved into my current place. It had everything else I wanted, gas hob with electric oven, enough power sockets, large rooms and the price was good, but I'm used to an electric shower. However the thermostatic valve here actually does work, winter or summer, toilet flushes or washing machine. This place was gutted five years ago, so it may be that all newer ones are better, or just that whoever renovated knew which models are worth the extra money.

  11. litch says:

    8 pints is a gallon, so you are getting 1 gallon in 65.6 seconds so you are getting less than 1 gpm (.91 actually), even the most restrictive low flow shower head is supposed to give 1.5 and 2.5 is the federal limit (a little over half what you are getting out of the tap).

    So there is definitely a problem.

    You need to measure the water pressure at the valve to figure out if it is a problem with the shower valve or the feed to it. Of course the only way to do that might be to shut the water off for the building, knock a whole in your wall, cut out the valve, put in a manual cut-off, re-enable the water, put a gage on the cut-off, test, replace the valve, repair wall, & re-tile. Actually your plumber is lazy, there is probably a shut-off for just the floor and a chance that there is a cut-off in place for your shower through a reasonably easily accessible place on the back side of the shower. If the problem is the feed none of that will do anything but cost you bucks gazoo and point the finger at whoever manages the water pressure for the building.

    • jwz says:

      There's no "back" to the shower. I am reasonably certain (from having been a victim of others' remodeling) that the only water cut-off is for the entire stack of apartments in which I sit. Which is less bad than the whole building, but still means that it's in a locked room in the basement for which getting the key is a big production.

  12. I can't believe you don't have separate isolation valves for each flat, never mind separate isolation valves for the bathroom! If this really is the case, some complete idiot plumbed the flats. More likely, the guy you talked to was trying it on big time.

    I'm not a professional plumber, but even I know that turning off the water to all the flats should never have to be done for such minor work.

    If you really can't isolate your flat, see if a plumber would be happy to use pipe freezer (I'm not sure whether this is recommended for mains pressure, so ask a professional) or something like that to stop the flow of water long enough to get some isolation valves installed, which cost next to nothing. Then they can have a good tinker with your shower and see if they can do anything without having to knock through the wall.

    If the valve is replaced and you have no improvement, it's the plumbers fault for not cleaning the pipes out, or choosing a really shitty replacement. Even temperature restriction valves shouldn't limit the pressure that much, especially if you have really good steady pressure from both taps in the sink.

    I'm assuming that is a mixer shower fed from your hot and cold water supplies, like it appears to be, and not an electric one of some kind. I also know nothing about American law and temperature restriction.

    Oh, and one more thing. Try closing the cold shower valve about half way and see if that makes any difference. Also, there looks like there's a third bigger valve there - have you tried fiddling with that, I don't know what it's for?

    • elusis says:

      Don't know what world you live in, but I have had this kind of situation in all kinds of places I've lived - apartment building turned condo in Denver, both apartment buildings I've lived in since moving to the Bay Area, etc. Generalizing from one person's experience is never wise, but I think I have *yet* to live in an apartment building where there are isolation valves for each unit.

      • Probably varies from country to country. littlejenny123 is from the UK like me, and it's common here even in multi-occupation buildings for each individual residence to have a separate billable water supply and independent heating. So you'd expect to find an isolation valve in the bathroom or in the kitchen (for the whole residence). Other arrangements are possible, but they're not normal here. I suppose a more US type arrangement might happen in what we call "tower blocks" with say eight floors or more. But those are rare.

        It turns out that modern cultural variation concentrates on these mundane differences in convention, the whole world watches The Simpsons and drinks Coke but we disagree about which position is naturally "off" on a light switch.

        • elusis says:

          For the record, the toilet paper should unroll from the top of the roll.

          • I agree on the toilet paper :-). And yes, I'm from Planet UK. I live in a house, where I've installed valves for isolating the bathroom, kitchen sink, and washing machine all separately. Costs next to nothing and makes maintenance much easier, which is why I'm surprised this isn't more common everywhere.

  13. mhoye says:

    Turn the two screw-valves on either side all the way in; this should turn off the water to the main valve. Then, open the main valve up. There will almost certainly, on the inside of that shower valve, be a screen filter of some kind that limits the throughput. Pop it out, that's its only job. Scrub the other bits you've pulled out clean with an old toothbrush or something, consider replacing the seals if they look old (those parts are cheap) and put it all back together.

    Consider snaking that pipe while you're doing all that, if you have those tools to hand.

    If you'd prefer to get advice from somebody with a lot more experience than I do and have a hardware store, Home Depot or Rona thing in your area, take these pictures (on the back of your digital camera will do), go to the plumbing section of the nearest one of those things, find the oldest guy there and show him the pictures, and tell him what you want to do. In my experience, old guys will tell you what you should actually do yourself to fix it for real, rather than just tearing it all out and replacing it at huge expense.

  14. hadlock says:

    I'm assuming you did this already, but you didn't mention it in the post, so I'll point this out. Have you tried unscrewing your shower head and testing the rate of flow that way? Shower heads screw off in about 10 seconds. This is a good time to upgrade your shower head while you're at it.

  15. rog says:

    Is the sink big enough to bathe in?

    Just thinking outside the box :p

    • argonel says:

      If thinking outside of the box is desired browsing would probably give an example of someone who ran a hose from their sink to the showerhead...

  16. nightrider says:

    I've had some minor self-plumbing experience, and I'm jumping on the "find a second opinion" bandwagon. Sounds like debris in the valve could be a culprit, but it also sounds more likely that tweaking the settings on the existing valve is an option, and you just gotta find a guy who knows his shit & is willing to help you out.

    My resume:
    I've repaired and replaced toilets, repaired weak/broken ceramic sink valves, installed garbage disposals & under-sink water filtration systems, replaced crushed faucet gaskets, and even been so bold as to pull out flow-restricton valves from shower heads.

  17. jferg says:

    Frequently the showerhead also has a flow regulator in it - usually it's just a piece of plastic right where it screws onto the pipe coming out of the wall that you can grab with a pair of needlenose pliers and pull out.

  18. pyrop says:

    Possibly terrible idea: Figure out an appropriate point of disconnection and backwash it.

  19. I've been in a similar situation, except one of the workers actually knocked off one of the valves while the building's super was away on vacation. We ended up improvising a thru-hull plug and for a few weeks before I could schedule a water shutoff I had a water pipe on the 5th floor plugged with a piece of wood on my mind.

    When the water was shut off my plumber installed a local shutoff and replaced all the fixtures. Things I did not know before that:

    1) if you pay a few bucks more, you can get ball shutoff valves instead of crappy gate valves (whatever you do, don't overtighten gate valves and don't leave them half-closed).

    2) Modern mixing valves in showers can limit temperature, rendering the old toilet flush trick impossible.

    3) You don't need to take apart the wall to replace the mixing valve - you can get a bigger cover plate instead.

  20. krick says:

    You need to get the incredible head shower head. I swear by them and have installed them in every place I have ever lived. They give a great shower, no matter how shitty your water pressure happens to be. You can usually find them locally at Home Depot or Lowes for under $10.'s also a cheaper model without the integrated cutoff valve...

    • volkris says:

      Personally, I hate these things.

      It's like they try to give a penetrating spray but fail, so what you get is something too hard to be a gentle mist but too soft to be a decent blast. That middleground is amazingly annoying.