weird water pressure

The shower water seemed normal for the first four years we owned our house but lately it's been acting weird.
The water pressure will start out fine. Then suddenly it will drop off and very quickly the stream will turn into a dribble, oftentimes stopping completely.
To get it to go again, I have to get out of the shower and turn on the faucet. The faucet water will start out slow then a second later will kick in. Just as the facet kicks in, the shower will start up again.
Can anyone tell me what's going on?
Brian
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Perhaps you have a pressure balanced faucet and the cartridge is become clogged.
Have you had any plumbing work done recently? It can dislodge particals that lodge elsewhere. Do you have copper or steel pipes? Galvinized steel plumbing is a major source or rust and strange flow patterns at elbows and tees.
Sounds like you have a rust ball shuttling back and forth across a Tee pipe connection acting like a valve. If it flows toward the shower, pressure is lost in one supply and the pressure balance valve shuts it all down. Running the sink forces the plug in the other direction but it takes a bit of flow before the shower unplugs too. Do you hear any other noises from the pipes like valve flutter when there is no valve?
Probably in the hot pipe since it is common to use 1/2" for hot and 3/4" for cold. The smaller diameter holds less water so the hot gets to the destination faster but it also clogs more easily.
If you have steel pipes and upon inspection see rust on the outside especially near the threaded connections, this is just the tip of the iceburg. Not much you can do to fix it besides make a good guess where the obstruction is and tear it apart and replace with new pipe.
Try taking the shower valve apart then run hot and cold water out of it while open to flush debris then try again. Replace the cartridge if applicable and check with the manufacturer, many have lifetime guarantees and you will get the part for free.
If you can open a faucet outside and connect a hose (from a friendly neighbor) to the sink, you can back flush the whole system but this might just move the problem elsewhere if it is rust based.

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I get that sometimes, but it's the city water supply on the fritz. I think it has something to do with switching from one pump to another. So ask your neighbors if they have the same problem.
What happens if you don't turn on the sink faucet? Does it come on anyway? I guess I am wondering if the faucet is solving the problem or if it is just a matter of time. Next time, can you yell to have someone turn on the kitchen sink?
Could it be something silly -- like four years ago the kids were in diapers but now they are flushing another toilet while you are in the shower? Or, maybe there's a housing boom where you are and their isn't enough water flow?
Are you on a well or on a public system?
If it a whole house issue,
If you have a well, it might be a bladder tank needing air.
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City water, or a private well?
--
Regards,
Doug Miller (alphageek at milmac dot com)
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Should have specified that I have a private well.
And, when I hit the faucet I hear what I am taking to be the water pump kick in.
I was messing around with the water softener not too long ago, but it is scheduled to run late at night.
Otherwise, I'll run through the list of suggestions in this thread and see if I can narrow it down.
Brian
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whole house filter plugged. It would have enough back pressure to satisfy pumps pressure switch and shut down pump. Then when enough water filtered through the filter finally, the pump would start up again. Turning on other faucets would seem to expedite the movement of t he water through the filter. I hadn't realized that I had a whole house filter as I had recently purchased the house. About a year later, had the same problem again but this time it was a bad motor on the pump. Wouldn't start back up after running for a while until it had cooled down a little. That was a real problem...just try to find someone to work on a shallow well pump located at the bottom of a 10ft deep, 4ft x 6ft pit. No well company would touch it...thank God for a 40 yr old son. However that was the last time...next time we go to drilling a deep well...my son was crippled up for a month after working in that hole.
Tom G.
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most well companys wont we are about the only ones left in maryland that will go in a shallow well pit.it can be a huge liabilty issue.we are the only ones that will come to your house and do a free estimate. what ever happend to customer service? scott
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This is just a guess, but do you think your pump coul have a bad checkvalve. If you used a certain qualtity of water, you would empty your bladder tank. It would turn the pump on. If the check valve was bad, there might be a lag as you pump water back up the pipe -- esp. if you had a pin-hole somewhere.
Also, when you open the sink, put your hand over the sink and see if any air is moving. If it's blowing air, it might mean that water is coming up the pipe and just hasn't reached it.
This is just a guess but it's all I can think of that would give that set of symptoms. Good luck with it.
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snipped-for-privacy@hotmail.com says...

In addition to the other suggestions, your tank may be waterlogged. Observe how rapidly the pump cycles on and off while water usage is high, e.g. while someone's in the shower, or while the washer is filling.
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On 29 Mar 2006 16:03:03 -0800, " snipped-for-privacy@hotmail.com"

Depends on whether you're right about having to get out and run the faucet, or if it eventually will kick back up again if you just wait in place. If it eventually comes back by itself, then I'd check all your filters and the pressure tank.
If it stays off/dribbling forever unless you run another fixture, then I'm thinking a bad valve or moving obstruction in or near the shower. In that case, try taking the shower head off for starters, and if that doesn't help, and there's a tub, flipping the diverter back to tub mode.
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You know what? Turns out it was the time not the action that restarted the water. Last night when the water stopped I got out, went to the faucet, and pretended I was turning on the water. Just then the water kicked in.
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Well at least one thing eliminated.
Instead of taking a shower, turn your bathroom and kitchen faucets on full blast and wait a bit and see if the problem is shower-specific or if other water usage causes the same problem.
Good luck.
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Sounds like your pressure swithc on the pump is out of adjustment, Set it to come on at a higher pressure. This way, as the pressure tank is drawn down, the pump will come back on before the tank empties. Or you may have a waterlogged pressure tank.
At first it sounded like a pressure balanced anti scald shower valve, but now it sounds lioke a well tank/pressure switch problem.
Stretch
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How would one go about adjusting the pressure switch on the pump? The problem is I don't see a switch anywhere near the pressure tank or at the top of the well. A cursory check on the web didn't reveal anything except for a complicated-sounding procedure for increasing the pressure in your tank via compressed air.
Someone else mentioned a checkvalve. Where is that?
Last night the shower turned off and wouldn't go back on again until I hit the faucet. This time I used the downstairs kitchen faucet. When the water kicked in it was accompanied by a "clung" sound downstairs. Dashed down there in time to hear the pressure tank filling up.
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