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Periodic Bad Water Pressure Q&A #3
FAQs help diagnose & fix water pressure that comes & goes

Questions and answers to help diagnose & fix intermittent or periodic loss of water pressure:

Here is our second set of FAQs on finding & fixing the cause of unexplained, oftren sudden but temporary drops in water pressure or intermittent but complete loss of water pressure.

This article series explains how to diagnose periodic or intermittent loss of water pressure either from municipal water supply piping or periodic or intermittent loss of water pressure from a private well. The process of diagnosis and the procedure for repair are explained.

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Intermittent Bad Water Pressure Diagnostic FAQs

Copper tubing on pressure control switch (C) Daniel Friedman

These questions and answers about why water pressure (water flow rate) seems to come and go in a building or in parts of a building were posted originally at WATER PRESSURE INTERMITTENT LOSS - home - be sure to see the diagnosis and repair advice in that article.

MUNICIPAL WATER PRESSURE DIAGNOSIS

WELL WATER PRESSURE DIAGNOSIS

On 2020-01-03 by (mod) - smaller ID of PEX affects water pressure or flow rate

Will

Please find our entire discussion and a detailed reply to your last comments now found at

WATER SUPPLY PIPE DIAMETER vs FLOW

And let me know what you think and what you find as that will help other readers too.

On 2020-01-02 by Will

Also, PEX 1/2" seems to maybe have a slightly smaller internal diameter than copper 1/2" due to the thickness of the pipe wall.

On 2019-03-07 1 by Marv

I have an underground cistern that stores water and a shallow water pump that pumps to a pressure tank. The system will regularly lose pressure at the house. Most times the pump is still running and has water with pressure when I open the prime valve on the pump. If the valve is open it will shoot water with good pressure out of the valv

e. By opening and closing the valve rapidly, the water will flow and the pressure tank will fill and all is well for awhile. Where is the likely spot to check first?

On 2019-01-26 by (mod) -

It might be worth hiring someone with a camera to inspect the entire wellbore for damage that could be letting soil into the well. That will also allow you to determine how far your pump is off the bottom of the well. Low flow rates and low water in the well can also increase turbulence and silt and degree-level.

Do let me know what you're told and we might be able to have other suggestions.

On 2019-01-25 by Paul

Thank you so much for your assistance! It seems that changing the filter has corrected the flow problem. I will certainly look into why the filter clogged so quickly.

On 2019-01-25 by (mod) - clogged sediment filter

Paul

A clogged sediment filter can certainly explain reduced order flow and pressure. However once the filter is clogged I would not expect the system pressure and flow to get better on their own until the filter cartridge is replaced. If you're having frequent rapid clogging problems at a sediment filter you probably need a much larger filter system and you might need to investigate the sediment source to be sure that the well casing is not damaged.

On 2019-01-25 by Paul

Is it possible that the "clog" is the sediment filter? Even though I only changed it a month ago. I have removed the filter and replaced the canister. I do not seem to have a loss of flow at the faucet now. Another interesting thing is that when I grabbed the filter, the whole palm of my hand turned black. I am going to replace the filter with a new filter and see if I get the loss of pressure/ flow again.

On 2019-01-24 22:46:03.723784 by (mod) -

I think you're describing clogged piping somewhere in the system; if pressure is equally weak for both hot and cold water then the clog or problem is ahead of the water heater.

The other common cause is low recovery rate or a low flow rate into the well.

On 2019-01-24 by Paul

I am having problems with water pressure in my house. I have a well system that is roughly 15 years old. We suddenly ran into low pressure problems in the shower and at the kitchen sink. I began by checking the pressure switch. It is a 60/40 switch. But it was clicking on around 32 psi and off about 56 psi.

I adjusted the switch to work correctly at 60/40 psi again. Now, when we use water and the pressure gauge drops to about 50 psi, there is very little pressure in the shower and other fixtures. If I kick the pressure switch on and bring it back up to 60 psi the pressure seems fine again. It is those times when the pressure at the switch/gauge does not drop low enough to kick the pump on that we have low pressure.

For example, I am running water at the sink and someone flushes the toilet. But if you drop the pressure to the 40 psi again and the pump kicks in there seems to be good flow at the fixtures.
Thanks for any advice you can give.

On 2018-07-20 by (mod) -

It's possible that the air charge is missing or too low in your pressure tank

On 2018-07-20 by AKing

We are on well water. Our water pressure in the house runs fine and then will taper off a little and then return to normal over and over. It only does this when we are running water in the house. Both the faucet near the well and the barn run normally. We have had our well checked and everything checked out normally there.

But when the water tapers off in the house, it sounds like water runs out of the pressure tank in the well rapidly. Any ideas?

On 2018-06-12 by (mod) -

If you have good water pressure when only one fixture is running and very poor water pressure when more than one is running that's telling us that the flow rate through your piping system is very poor. Typically that's because the water supply piping system is clogged. Your plumber can make that assessment and will either replace some piping sections or look for and replace an actual blockage.

On 2018-06-11 by Dee.

I have a septic system and I am having water pressure issues in one of the bathrooms in my house and if I flush a toilet sometimes I have no water pressure can somebody please tell me what could be causing this very difficult to take a shower when the shower will not come on it’ll only drip

On 2018-04-21 by Anonymous

Perhaps the pressure control switch is sticking due to debris clogging, only showing up when there is a rapid demand

On 2018-04-21 by John

Very strange problem I’m having! I have a shallow well pump.......everything is fine until there is a high flow demand.....

.it seems that if someone is using the shower and I turn something else on like a faucet the water flow stops for just an instant then I hear the pump come on and the pressure returns to normal......this didn’t happen in the past......not sure what the problem could be?

On 2018-04-03 by (mod) -

Check for a debris-clogged pressure control switch sensor opening or clogging in the tube conducting pressure to the switch base.

On 2018-04-03 by Danae

We have an odd situation that is quite frankly stumping us. We are on well water. We have good water for a while and then it will taper off and then come back in a burst and that cycle will continue. however this morning, there was only a trickle of water and was not coming in strong bursts like it is now.

On 2017-12-16 by (mod) - pump control or pump motor problem

Brit

I speculate that there is a control or pump motor problem. Sometimes when a pump motor is failing and perhaps overheating, it may have trouble starting and may draw high current (amps) that might dim your lights.

If the pump and lights are on separate circuits (as they should be) and the pump dims the lights then there is a tremendous current draw happening at the electrical panel. I would ask for help from an electrician.

She might start by a visual inspection in the panel for burning or trouble signs, then move on to the pump circuit. By measuring the current draw on the pump circuit one can get an idea if the pump motor is in trouble.

Jason

When we have good water pressure in part of a building and bad in another that itself is diagnostic, and suggests just what you've guessed: a clog or valve problem somewhere in the poor-pressure side of the piping.

The brief higher-pressure flow is typical when there is decent water pressure in the piping system but an obstruction in flow. I speculate that when you first open the tap a bit of water in the poly (plastic) pipe that is downstream from the point of blockage spurts at good pressure out of the faucet.

Then the system flow drops because of the obstruction. One might speculate (a bit wildly) further that the duration of decent flow allows a guess at how far back in the piping the actual blockage has occurred. Longer flow (your 7 seconds is pretty long) says there must be a branch point and blockage in supply piping rather far back from the point of use.

Application of Binary Search Technique to Finding a Plumbing Supply Pipe Blockage

If a plumber doesn't see something obvious she might try making a couple of test cuts and flow observations in the bad piping side to perform a binary search to home in on the point of blockage.

The binary search is mathematically the most-efficient way to look for a needle in a haystack in the least number of searches.

Divide the bad piping length in half. Cut it there. Diagnose which side of the cut has the problem. CUt that side in half, etc.

On 2017-12-16 by Brit

Hi, we have a well for our water supply. Lately our water will sometimes run, but then it will stop for 3-5 mins and then turn back on with a surge of pressure. Sometimes I notice a surge in the lighting when this happens. Any ideas?

On 2017-12-08 by JasonC

Dan - I am having an issue today that I am at a loss of words for. The issue is that half of the house has low hot water pressure and the other half is fine. This is also poly pipe.

When I turn on the hot water on the left side of the house (ie. kitchen sink, bathroom faucet, shower), it runs fine for about 7 seconds and then gets hit with a small shock and hot water flow is reduced to a third. The 7 seconds is further reduced if I keep turning it off and on. After a few immediate on and offs, it’s all low water pressure until leave it off for a few minutes.

The right side of the house works completely fine. It’s almost like something is clogged in the pipe on the left side. The water is all coming from the same water heater. Any ideas??

On 2017-12-16 by (mod) - pump causes lights to dim

Brit

I speculate that there is a control or pump motor problem. Sometimes when a pump motor is failing and perhaps overheating, it may have trouble starting and may draw high current (amps) that might dim your lights.

If the pump and lights are on separate circuits (as they should be) and the pump dims the lights then there is a tremendous current draw happening at the electrical panel. I would ask for help from an electrician.

She might start by a visual inspection in the panel for burning or trouble signs, then move on to the pump circuit. By measuring the current draw on the pump circuit one can get an idea if the pump motor is in trouble.

On 2017-12-16 by Brit

Hi, we have a well for our water supply. Lately our water will sometimes run, but then it will stop for 3-5 mins and then turn back on with a surge of pressure. Sometimes I notice a surge in the lighting when this happens. Any ideas?

On 2017-12-16 by (mod) - How to use a Binary Search Method to Find a Water Supply Pipe Blockage

Jason

When we have good water pressure in part of a building and bad in another that itself is diagnostic, and suggests just what you've guessed: a clog or valve problem somewhere in the poor-pressure side of the piping.

The brief higher-pressure flow is typical when there is decent water pressure in the piping system but an obstruction in flow. I speculate that when you first open the tap a bit of water in the poly (plastic) pipe that is downstream from the point of blockage spurts at good pressure out of the faucet.

Then the system flow drops because of the obstruction. One might speculate (a bit wildly) further that the duration of decent flow allows a guess at how far back in the piping the actual blockage has occurred. Longer flow (your 7 seconds is pretty long) says there must be a branch point and blockage in supply piping rather far back from the point of use.

Application of Binary Search Technique to Finding a Plumbing Supply Pipe Blockage

If a plumber doesn't see something obvious she might try making a couple of test cuts and flow observations in the bad piping side to perform a binary search to home in on the point of blockage.

The binary search is mathematically the most-efficient way to look for a needle in a haystack in the least number of searches.

Divide the bad piping length in half. Cut it there. Diagnose which side of the cut has the problem. CUt that side in half, etc.

On 2017-12-08 by JasonC

Dan - I am having an issue today that I am at a loss of words for. The issue is that half of the house has low hot water pressure and the other half is fine. This is also poly pipe.

When I turn on the hot water on the left side of the house (ie. kitchen sink, bathroom faucet, shower), it runs fine for about 7 seconds and then gets hit with a small shock and hot water flow is reduced to a third.

The 7 seconds is further reduced if I keep turning it off and on. After a few immediate on and offs, it’s all low water pressure until leave it off for a few minutes.

The right side of the house works completely fine. It’s almost like something is clogged in the pipe on the left side. The water is all coming from the same water heater. Any ideas??

On 2017-10-16 by karen1

we have a well. while running water anywhere in the house, washer pressure is good but suddenly will stop for about 10 sec. and then start running again. any ideas out there?

On 2017-09-24 by (mod) - when the bad water pressure is only on the hot water side

If the problem is hot-water only then we don't suspect a pump, well or system problem. That leave us to follow the hot water piping form the point where the cold line branches off to send incoming cold through the water heater, forward to the first hot water fixture.

On occasion a deteriorated dip tube in the water tank can produce enough debris to clog the cold inlet or hot outlet. I'd start by seeing if I have water pressure into and then out of the water heater.

On 2017-09-24 by Anonymous


No there isn't

On 2017-09-24 0 by (mod) - check the anti scald valve

Chris,

Is there an anti scald valve or mixing valve installed that could be sticking or malfunctioning?

On 2017-09-24 by Chris

Once in awhile the hot water pressure throughout the house is at a trickle (cold water is fine). A few times we disconnected the the flexible pipe coming out of the water heater put it in a bucket to test and the pressure comes out fine. After reconnecting, the pressure throughout the house is back to normal.

Other times without disconnecting it, the pressure will come back after several hours. Almost seems like the water in the tank needs to purge?! Neighbors don't have any problems.

On 2017-08-20 by (mod) - effect of work on the water mains on temporary pressure loss

San,

I can but guess that the municipal system was being worked-on or adjusted - something to check with your neighbours or with the city itself.

On 2017-08-20 1 by San

Have city water... One day my water pressure went low throughout the house..2 days later water pressure was back to normal... What happened?... Will It happen again?...Is this a issue for city public works department?...help

On 2017-08-14 11:09:09.881120 by (mod) -

Dan,

If you have hot and cold water at other fixtures in the same building then I would be looking for a valve that is closed or a pipe that has become blocked. Generally I follow the piping from the last common point where both the fixtures that have water and the fixtures that don't are being fed and then I move on from that point towards the fixture that does not have water looking for a valve.

If there are no valves I also check the faucet strainer for clocking and if that is removed and they're still no water I check the shut offs under the sink or at the toilet. If none of those find a problem then there may actually be a blockage in the pipe itself and I need help from a plumber

On 2017-08-14 by Dan

I have two problems
1st. Hot water going to kitchen in a home is not having any pressure .I just replace a section that was 1\2 " too 3\4" but the problem is still there.
How can I fix this

2nd . cold water feed going to back bath near water heater is no existent .how can I fix this feed is a 3\4 reduced 10 ft from bath

On 2017-06-17 by (mod) - pump won't stop

Rex,

a really good diagnostic article for the problem you describe can be found at this website by using the search box just above to find

WATER PUMP WONT STOP RUNNING

Where we list the common problems and repairs for water pump that can reach cut off pressure or won't stop running

On 2017-06-17 by Rex

Well pump will not build over 25 psi and will not shut off,it is a jet pump.

On 2017-05-22 by (mod) - bathtub spout can easily run 5-8 gallons of water a minute

Trains

A bathtub spout can easily run 5-8 gallons of water a minute - as you noted, the strongest spout int he home; that itself, combined with poor water pressure or small-diameter or clogged water pipes would explain what you are seeing; adding a macerating pump - that sounds like a drainage system or grinder pump used for a toilet or to pump wastewater up to a building drain that's at a higher level - wouldn't affect the supply pressure.

On 2017-05-22 by trainsme

I had a bowl with a macerating pump and a vanity installed in my basement. When I run my bathtub " the strongest spout"
While its running I lose water pressure everywhere else in the house. Any ideas?

On 2017-04-30 by (mod) - is the municipal well pump being turnde off?

Start by asking the operator of the well if they are turning the system off or throttling back on water supply, perhaps to protect a marginal water well. It's also possible that the well flow rate has deteriorated.

On 2017-04-30 by Rachel

We are on community well, we all have individual boxes shut off box, so we don't have leaks we just don't know why we lose water some days everyday amd sometimes once a wk. have any clues?

On 2017-04-29 by Joe

My well is cutting on at 30 psi and not cutting off until 120psi. The contacts on the pressure switch look like new but I am thinking maybe the diaphragm is clogged or broken. Is this correct or do I have another problem?


...

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