Sudden drop in water pressure on second floor
April 11, 2009 8:27 AM   Subscribe

What can I do to investigate a sudden drop in water pressure (or flow) in the second floor only of my house before I call a plumber this Monday?

I've already seen this question, but I bought this new two storey townhouse three years ago and all has been fine up until yesterday.

Basement and first floor pressure are fine in all sinks and the powder room toilet. But the second floor water sources have been weak since yesterday. The flow from the bathtub tap is markedly decreased, the sink is a little softer, too, and the toilet flush is definitely weak.

Given the sudden onset and localization, could this be a leak? (Oh, I really don't want to call a plumber out on a holiday weekend if I can help it, although I know that if this could be a leak, I should move fast). Or could a slowly building blockage show no signs until it just reached a critical point yesterday?
posted by maudlin to Home & Garden (9 answers total)
Best answer: Doesn't sound like a local problem to me. First thing I would do is phone the water district. They do things like clean out hydrants, repair lines, etc., all of which can reduce pressure to the whole area.
posted by weapons-grade pandemonium at 8:34 AM on April 11, 2009

Response by poster: Thinking about it, the toilet flush depends on letting water from the cistern flow into the bowl, while the cistern is refilled from the pipes, so does pipe water pressure even affect the strength of a flush?

I just checked: The downstairs toilet takes 25 seconds to refill the cistern; the second floor toilet takes 40 seconds. They're the same model, although the second floor toilet seems to drop the stopper almost immediately after flushing, so that seems like a local mechanical problem. Still, the refill rate is very different, and backs up my impression that the bathtub tap is also slow.

On preview: weapons-grade pandemonium, are you saying that if the overall water flow is affected, it may affect the second floor much more obviously than the first just because of gravity?
posted by maudlin at 8:45 AM on April 11, 2009

Response by poster: D'oh!!! and *facepalm*

There's water main work going on at our street corner. I didn't find out what it was until yesterday, so yes, now this all makes much more sense. I'll ask my neighbour if they're experiencing the same thing.
posted by maudlin at 8:52 AM on April 11, 2009

Dirt will often get into your water lines when they do these things, so filter or boil your water, or drink bottled water for the next few days.
posted by weapons-grade pandemonium at 9:09 AM on April 11, 2009

Best answer: so does pipe water pressure even affect the strength of a flush?

Only marginally: the main flushing action comes from gravity (unless you have a pressure-assist toilet, of course), but usually as the cistern refills some water is sprayed down into the bowl to refill it; strong water pressure and high flows will give a little extra water volume to the flush -- but this is minor compared to the main flushing action.

My money is on clogged pipes from the nearby water main work, but that's just a guess. Your second story will always be a few psi less than the first, because of the elevation difference, but that shouldn't be noticeable at all, unless your water pressure was really marginal to begin with. (Normal city water pressure might be 60psi; you aren't going to notice the difference between 60psi downstairs and 57psi upstairs in any normal household use.)

Assuming that the faucets upstairs and downstairs are similar, you can get an approximate measurement of the flow with a bucket and a stopwatch -- that might be more useful than your current general impression of slowness. A 5% difference isn't a big deal, but a huge drop in flow is definitely worth getting a plumber out to have a look.

Dirt will often get into your water lines when they do these things, so filter or boil your water, or drink bottled water for the next few days.

The chlorine in the water should be adequate to kill any organisms that get in -- dirt itself isn't dangerous, but a lot of it (enough to change the color of your water) can be an indication of work on the water line or other issues, and high turbidity can push or exceed the limits of the chlorine's ability to deal with contamination. Most cities are pretty conservative about this stuff (there's a lot of oversight of drinking water, and it's a big embarrassment when a bunch of people get sick), so I'd start by phoning the city if you are concerned about it.
posted by Forktine at 9:38 AM on April 11, 2009

Response by poster: I've measured the toilet cistern refill rate on both floors -- 25 vs 40 seconds -- so that does seem like a large difference. However, if my neighbours are noticing similar differences, then I'm less inclined to call a plumber. The city has been digging out there for a couple of weeks with no change in water pressure until now, so I wonder if they screwed up something on Friday, then went home for the holiday weekend.

I just called the reporting line for Toronto Water and they have confirmed several reports of low water pressure in my neighbourhood over the past couple of days, so the repairs still seem to be the likely culprit. I have a number to call Monday so that someone can come over and check if needed.

I always use a Brita pitcher for my water, so this should probably be a good enough filter.

posted by maudlin at 9:57 AM on April 11, 2009

If you have the time, I'd suggest measuring flow at the bathtub faucets. Are you completely, 100% sure that both toilets have the same size cistern? That neither has a water inlet that is partially clogged with minerals? Whereas the bathtub faucet is unlikely to have an aerator that can get clogged, and are often the same size as your household pipes, giving you a more accurate measurement of flow.
posted by Forktine at 10:11 AM on April 11, 2009

If this continues after the nearby work is finished, and after your neighbours return to normal service, DO bug the city about it. (Assuming that Toronto is the same as Ottawa in that they're responsible for everything up to and including the meter.)

When our mains were replaced a few years ago we had a severe drop in pressure (tap on downstairs meant barely any water upstairs). It continued after the work was completed. They city came and vaguely looked at it and blamed the age of the house / interior pipes / whatever they could to prevent them from doing any actual work - essentially they didn't want to dig up the newly paved road. We weren't vocal enough about our concerns and didn't raise it any further and lived with the very low pressure.

A year or so later we had some house renovations done which involved shutting off the water and relocating the meter. Plumber brought the meter to us and showed that it was pretty much clogged with dirt from the water main reconstruction. He said it's not uncommon and the city really should have at least taken the meter out to check the pressure when we complained, but they obviously try to avoid doing any work they're not forced to do. Life was much easier after this.
posted by valleys at 10:32 AM on April 11, 2009

Response by poster: Both toilets are American Standard, 6.01 Lpf/1.6 gpf. I have only one bathtub in the house, so I've run a comparison of full-blast filling of a 1 litre jug from each sink: First floor: 6 seconds. Second floor: 6 seconds. I think the container may be too small to show enough of a difference.

But the water pressure is good enough for now (knock wood!) and I have a better idea of how to assess the situation and who I can contact in the city government. Thanks again, everyone!
posted by maudlin at 5:01 PM on April 11, 2009

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