Low Pressure issue- i'm stumped

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rooooney

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I'm rehabbing a home with one 2nd floor bathroom. The bathroom had terrible water pressure if any one fixture was running, and the shower always had bad pressure. When the walls were open I realized the whole home was running off 1/2 pipe. I replaced everything with 3/4 inch from the meter stepping down to 1/2 inch at the fixture. Currently the bath still has poor pressure regardless of whats running so i planned on replacing the fixture, although it looks new. When I put a gauge on the cold water feeding the vanity sink it reads 65 psi, when i flush the toilet the sink drops to 5, sometimes 0 psi. The hot water even loses pressure dramatically when I flush the toilet. If i shut off the toilet water inlet valve and have the cold water running in the 65 psi vanity it also drops dramatically when i turn on the bath water. I'm at a loss, i'm far from a trained plumber but Ive run complete water lines in 5 homes at this point without ever experiencing anything like this. Looking for any advice.
 

Reach4

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When you flush the toilet, both hot and cold on the lavatory are affected?

How is flow in the hot in the kitchen affected by the tub cold running?

I am wondering if there is a whole house cartridge filter that is clogged up.

Or if the pressure of everything in the house drops, including the outside hose spigots, then the pipe from the water main might be the problem.
 

rooooney

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When you flush the toilet, both hot and cold on the lavatory are affected?

How is flow in the hot in the kitchen affected by the tub cold running?

I am wondering if there is a whole house cartridge filter that is clogged up.

Or if the pressure of everything in the house drops, including the outside hose spigots, then the pipe from the water main might be the problem.

Th aka. currently the only thing plumbed in is the tub, vanity and toilet, nothing else is in the system. I’m just confused why it’s reading such good pressure then everything drops when one thing is used. I’m going to plumb in the kitchen sink, a hose and washer machine today and see if that helps. I also have a feeling this tub could be the issue. It doesn’t leak but makes a gurgle sound when used and always has low pressure regardless.
 

Reach4

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Th aka. currently the only thing plumbed in is the tub, vanity and toilet, nothing else is in the system. I’m just confused why it’s reading such good pressure then everything drops when one thing is used.
If you supplied the house with 1/8 inch ID pipe, the pipes inside would still read 65 psi when no water is being used.

If you are up on electronics, even a high-resistance resistor has no voltage drop when there is no current through it.

You want to figure out if the restriction is before where the water comes into the basement/crawlspace, or if it is later. If the restriction is before the basement, you will need new piping from the main. That will be a shock to your budget. :-(
 

Tuttles Revenge

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Agree with Reach4, you have a restriction of some sort. Maybe a water service that is really long or really long and old galvanized steel. Maybe a control valve that was only turned on part way to test but left that way. Maybe a meter valve that is turned on only partially.

I had a customer with a thousand foot 1/2 galvanized water service.. great pressure. But if you had the upstairs sink going and opened the sink downstairs, you would draw air into the faucet.
 

rooooney

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If you supplied the house with 1/8 inch ID pipe, the pipes inside would still read 65 psi when no water is being used.

If you are up on electronics, even a high-resistance resistor has no voltage drop when there is no current through it.

You want to figure out if the restriction is before where the water comes into the basement/crawlspace, or if it is later. If the restriction is before the basement, you will need new piping from the main. That will be a shock to your budget. :-(

That makes sense. Is there a way to figure that out? If I put the pressure tester in the line right after the meter? The only thing that isn’t new is the old shut off before the meter. Maybe that has an issue.
 

Reach4

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That makes sense. Is there a way to figure that out? If I put the pressure tester in the line right after the meter? The only thing that isn’t new is the old shut off before the meter. Maybe that has an issue.
Yes, that is the deal. If your line splits off to an outdoor hose spigot, you can mount a garden hose thread pressure gauge. You can take a movie of the gauge if you want to run around and turn things on and off.

If that pressure stays up, then you will know that the problem is between there and where the tee off to the water heater is. That is because your pressure drops in the bathroom are for both hot and cold water.
 

rooooney

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If you supplied the house with 1/8 inch ID pipe, the pipes inside would still read 65 psi when no water is being used.

If you are up on electronics, even a high-resistance resistor has no voltage drop when there is no current through it.

You want to figure out if the restriction is before where the water comes into the basement/crawlspace, or if it is later. If the restriction is before the basement, you will need new piping from the main. That will be a shock to your budget. :-([/QUOTE
Agree with Reach4, you have a restriction of some sort. Maybe a water service that is really long or really long and old galvanized steel. Maybe a control valve that was only turned on part way to test but left that way. Maybe a meter valve that is turned on only partially.

I had a customer with a thousand foot 1/2 galvanized water service.. great pressure. But if you had the upstairs sink going and opened the sink downstairs, you would draw air into the faucet.
I replaced everything off the meter with 3/4 inch cpvc. It the upstairs tub somehow was sucking in air could that mess the whole system up? It’s the farthest from the service entrance.
 

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I replaced everything off the meter with 3/4 inch cpvc. It the upstairs tub somehow was sucking in air could that mess the whole system up? It’s the farthest from the service entrance.
It is an indication of a problem elsewhere -- not the problem itself.

Did you have the pipe from the street to the water meter replaced? That is the one to worry about.
 

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Yes, that is the deal. If your line splits off to an outdoor hose spigot, you can mount a garden hose thread pressure gauge. You can take a movie of the gauge if you want to run around and turn things on and off.

If that pressure stays up, then you will know that the problem is between there and where the tee off to the water heater is. That is because your pressure drops in the bathroom are for both hot and cold water.
Yeah that’s what I did up at the vanity in the bathroom. I just put a garden hose attachment on the cold water side and watched it plummet when I turned on the tub or flushed the toilet. I’m going to try it closer to the meter and see how it moves, I love the camera idea, thanks.
 

rooooney

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It is an indication of a problem elsewhere -- not the problem itself.

Did you have the pipe from the street to the water meter replaced? That is the one to worry about.
That has not been replaced. Really hoping that isn’t my issue. But trying to figure out how to eliminate all other possibilities before it comes to that. Not sure how to determine if that needs replaced.
 

Reach4

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That has not been replaced. Really hoping that isn’t my issue. But trying to figure out how to eliminate all other possibilities before it comes to that. Not sure how to determine if that needs replaced.
I’m going to try it closer to the meter and see how it moves,
That's how.

If there is a lot of restriction in the service pipe, it can be gunked up with deposits, or a loaded concrete truck could have driven over the copper or lead pipe. Restrictions due to deposits and rust in steel pipe is likely. Magnet identifies steel pipe.
 

Jadnashua

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Depending on the age of the house, the supply from the street could be galvanized, and over the years, it starts to rust, often from the inside out. Eventually, it leaks, often around the fittings, but could be anywhere. Do you have spots in your yard that seem to be wet or greener than others along the path your water supply line goes? If it's before the meter, you might not notice a leak, but would notice your volume going down. Or, it could have become crimped if something drove over it. That normally isn't that common depending on how deep it is. It's possible a tree root might have messed with it say between a rock and a hard spot.

What size and type of pipe is on the inlet side of the meter? That may or may not be indicative of what's outside, but it's a start.

The type of shutoff valve could be an issue as well as it's condition. A gate valve could be stuck. If you open/close the main shutoff, does the handle stop, or just spin, and, does it actually shut the water off?
 

wwhitney

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I replaced everything off the meter with 3/4 inch cpvc.
So, 3/4" CPVC has a maximum inner diameter of 0.716", vs 0.785" for 3/4" type L copper. That's going to cause you some extra frictional loss compared to using copper, but nowhere near as bad as you are seeing.

I assume your meter is indoors in your climate. If you can easily plumb in a hose spigot or pressure gauge right after the meter, that's the easiest way to tell where the problem is. If that pressure gauge drops precipitously whenever you draw water, you know the problem is upstream of the gauge (the meter, the meter shutoff, the buried pipe outside). If that pressure gauge holds will little drop during flow, you know the obstruction is in your new work (most likely some debris that got trapped).

Cheers, Wayne
 

rooooney

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So, 3/4" CPVC has a maximum inner diameter of 0.716", vs 0.785" for 3/4" type L copper. That's going to cause you some extra frictional loss compared to using copper, but nowhere near as bad as you are seeing.

I assume your meter is indoors in your climate. If you can easily plumb in a hose spigot or pressure gauge right after the meter, that's the easiest way to tell where the problem is. If that pressure gauge drops precipitously whenever you draw water, you know the problem is upstream of the gauge (the meter, the meter shutoff, the buried pipe outside). If that pressure gauge holds will little drop during flow, you know the obstruction is in your new work (most likely some debris that got trapped).

Cheers, Wayne
Thanks - that makes sense.
I took your advice and put a gauge just after the meter, it reads 80psi. When I draw water anywhere in the house it drops to near zero. So sounds like i have an issue upstream. I did notice that the shut off valve before the meter in the metal pipe is very old and when i shut it off it leaked a little water out of the top of it near the crank. I'm going to have the city shut off the water and replace that , of that was obstructed i'm guessing that could cause my problem? If not I guess it;s time to start digging. Thanks again for the tips, this page is great.
 

wwhitney

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Yeah, if the shut off valve just before the meter is working poorly, it could fail to open fully and cause all the symptoms you are seeing. I guess extreme crud on a filter mesh on the inlet side of the meter would also explain your symptoms (a side effect of operating the valve?)

What can you see of the water lateral coming into your basement (I assume), can you tell what size and material it is?

Cheers, Wayne
 

Reach4

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I'm going to have the city shut off the water and replace that , of that was obstructed i'm guessing that could cause my problem?
While talking to the city folks, ask what they suspect based on what they have seen before.

You could try to send an electrical snake up the water line to see if you run into a sudden obstacle.
 
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