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WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER CONSERVATION MEASURES
WATER CONTAMINANT LEVELS
WATER FILTERS, HOME USE
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL CHLORINATION & DISINFECTION
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
How to diagnose & fix intermittent or periodic loss of water pressure:
This article 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.
If the building water supply stops and takes minutes to hours to recover, the municipal water system may have work going on outside of your building, or if your water is supplied by a private well, you may have problem with the well flow rate.
But the problem of lost water supply and pressure could be more mechanical and may be due to a problem right in your building itself, as we will explain..
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MUNICIPAL WATER PRESSURE DIAGNOSIS: If your water is from a municipal supply and the pressure or flow seem to vary or start and stop
Readers whose water pressure recovers when the pump cycles on, but find water pressure dropping without explanation when the well pump stops should
Also see WATER PRESSURE LOSS DIAGNOSIS & REPAIR and
also WATER PRESSURE STOPS, RETURNS - more details about intermittent water pressure and what to do about it.
WELL WATER PRESSURE DIAGNOSIS: If your water is provided by a private well and the pressure or flow seem to vary or start and stop
When you lose water pressure or lose all water supply for some time period but water pressure later returns or improves, check the possible explanations outlined just below. On the other hand, if you lose and do not recover water pressure in the building see Diagnosis of Loss of Water Pressure which Does Not Recover on its Own.
The following unusual water pressure case traced to a pressure regulating valve was described by Timothy Pearson, a senior plumbing designer in Charlotte, NC:
This poor hot water pressure problem had three senior level designers stumped as to a reasonable cause.
A young architect ... had a problem that we could only guess at: when he turned on the shower, lav, or kitchen sink hot water (both two handle and single handle arrangements) he got a steady stream of water from the spout/head. But after a brief interval water pressure slowed to a trickle.
When any other plumbing fixture valve, either hot or cold, was then opened, water pressure returned to a strong stream (pressure).
As this happened at every plumbing faucet this pretty much eliminated a clogged pipe possibility.
We wondered if there might be a large piece of debris in the water heater itself. This would explain that when any valve is turned on it equalizes the pressure and whatever debris (lighter than water) is moved thus allowing the pressure to increase? I have had a plumbing contractors’ license for 23 years and had my own firm for 10 years before I went back to college and graduated with a mechanical engineering degree (Thanks PM magazine and Julius Ballanco)
[We also speculated about another intermittent water flow blockage, a possible water tank bladder problem as we have seen odd water pressure behavior traced to that failure. - Ed.]
The young architect brought in pictures (see the photo above), what a difference when you actually see some of the system.
The previous owner had installed or had someone install a PRV [pressure regulating valve] in the cold water inlet to the water heater after the shut-off valve to the heater. We advised him to adjust the PRV to the point where it actually was not regulating the pressure through the valve at all. Problem solved.
I plan to go on a free Saturday at some point to verify that the inlet PRV is functioning correctly , and remove the PRV on the cold water inlet to the heater. I also intend to replace the gate valve with a ball valve and remove the 5 or 6 couplings on the hot water outlet piping.
Also its not being the smartest plumber, it is getting as much input to each problem or design issue from as many other people as possible that makes you a better designer, plumber, installer, etc. I am old enough to realize that anyone may make a suggestion that either will be better or different one from the one you had thought of regardless of the suggesting person’s experience. Sometimes someone else’s input triggers your realization of another solution.
-- Thanks, Tim Pearson
Impact of Sediment & Debris on Intermittent Water Pressure
This sequence of reader questions, moderator replies, and reader follow-up illustrate how we tracked down an "intermittent water pressure problem" to a problem with sediment, debris, and clogging water filters.
6/22/2014 Tom Evans said:
Okay, I have read everything I can find but am not seeing my exact scenario.
I should mention that flow is compromised in the entire system when it falls off
Most likely you are exceeding the sustainable well flow rate. Less likely could be a motor overheat or low voltage problem.
I wondered about that. assumed that that is what it had to be until today. The preassure in the tank will build when the pump is working even while the sprinkler runs. The pump does not shut off until the cutout pressure is reached. If the tank pressure is building then there must be water right? - Tom Evans
Well flow rate is made up of a complex of flow numbers at different depths, differing rates, and for different sustainable intervals. When you draw a lot of water you may see water delivered at full pump capacity until the static head is exhausted, then a slower flow rate that may slow even further after local water close to the well bore has become exhausted - DF
I think I understand what you are saying. If I understand correctly, if the flow rate in the well is reduced then the flow into the pressure tank would be reduced and so the flow rate to the hose is reduced. What I seem to be observing is that the flow rate to the hose and the house is reduced but the pressure tank is refilling in good order. Even when the pressure tank is at 60psi the flow to the house and hose is compromised after the hose has been running for ~15 minutes.
New data from this evening:
Try removing the filter cartridges to flush the system, then install new filter cartridges and flush further. - DF
[Flushing from a point downstream from the water pump & filters & tank and onwads to outdoors avoids further clogging of filter screens at indoor sinks & showers, though those too may need to be cleaned. ]
Reader follow-up: flushing out filters seems to fix the water pressure problem
Can I flush to the nearest hose bib? I don't have to flush thru the house, right?
Okay, test is ongoing but seems ot be woking more as you would expect it to. For the first ten minutes or so well and pump were maintaining tank pressure but not recouping to 60psi.
The last 10 minutes pressure has been dropping while the pump runs. I think this is an indication that "the static head is exhausted"? I am tempted to run the water till the pump shuts off (heat protection shutoff- if that is what you call it) it has happened in the past when we were clueless. This would show for sure tha we are simply running out of water in the well- correct?
Ran water thru near hose bib for 1hr 25min w/o spin down filter or solid canister filter in place. Very little loss of flow. Installed a "bubbler" to diffuse water stream after 1hrl flow was approx. 7 gpm vs 10 gpm when we began (w/o bubbler).
I have been using a solid filter that was supposed to be good for six months rather than a pleated filter that would need replacing every 3. I am wondering if this is a false economy and that the increased surface area of the pleated filter would address the flow slow down.
Put things back together and after 1/2 hr flow was back to its bad ol used to be. I shut off supply from the tank/pump and opened the spin down flush valve. Pressure restored. I am amazed that it could clog so quickly.
Indeed if the water supply system is picking up lots of sediment filters can clog quickly. For severe cases we need to install much larger-capacity filtration equipment, sometimes a settlement tank, or a cascade of filters handling particles of varying sizes (larger first).
Also check that the pick-up height of the foot valve in the well is not too close to the well bottom. This can happen if well casing damage permits soil to leak into the well, filling the bottom end of the well bore - something to discover by camera inspection of the well casing interior.
Finally, check and clean filter screens at indoor faucets and check for clogging at shower heads or other flow restrictors.
(Less common we've even seen debris clogging at stop valves in the piping system - moreso at some gate valve and globe valve designs than others.}
Continue reading at WATER PRESSURE STOPS, THEN RETURNS "on its own" or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs)
Question: Water pressure varies from very high to very low in just a few minutes
my water pressure gets real low then it gets real high and have full blast pressure and then it cuts back down and then in a few minutes it goes back to full pressure - David
Reply: diagnosing water pressure problems, where to start
Often when we find the water supply system misbehaving by showing intermittent pressure changes and surges I suspect that the pressure control switch is not working, perhaps because debris has clogged the sensor on the switch.
Your comment that the water pressure is varying from very low to very high in a very short time is very suggestive of a water-logged water pressure tank. See WATER PUMP SHORT CYCLING to diagnose this condition.
Otherwise, to help troubleshoot this intermittent water pressure problem you might want to take a look at our WATER PRESSURE PROBLEM DIAGNOSIS TABLE
Question: our water cuts out for about 45 seconds then come back on with the same or more water pressure as before
We have been having issues with our water. We have a well. and when we take showers or use the washer.. not so much with the tap but just things that use a lot more water our water cuts out for about 45 seconds then come back on with the same or more water pressure as before.
It's annoying but now more nerve raking thinking it could be something way worse or more costly! I don't hear the tank in our house clicking on and off constantly so I don't think its that but I will say there is lots of condensation around the tank and it has caused us to have a very bad mould problem in our spare bedroom.. with a 14 month old that is unacceptable for me. but could the condensation have something to do with our water problem possibly before hiring somebody to take a look at it. our tank says it needs a max of 100 psi for air pressure and it only has 70 psi.. not sure if that means anything or not since I am not very knowledgeable in the plumbing field? please help! - Krista
Reply: check your pressure control switch for clogging or just try replacing it
Krista it sounds as if a pressure control switch is sticking and not turning the pump on and off on schedule. A clogged pressure control switch could be at fault - if so it's not a major repair.
Question: Our pump runs when we are not calling for water, water flow slows and stops sometimes, and water pressure at the tank falls when we are not running water at all
I have a similar issue. First we experienced intermittent running of our well tank. The tank would run when we were not calling for water. We had the tank replaced and upgraded from 20 gallons to 35 gallons.
Our pressure switch is set at 30/50 psi. We were told that the valve(??) was bad because water did not shoot out and air was sucked back in when the tank was replaced. Since having the tank replaced, the psi still decreases when we're not running water. In addition a new problem has started. Our water slows down and then stops completely for about 15 seconds during various times of the day (showers, washing dishes, etc.) and the water will spit at times (running faucets or when the toilet fills up). We verified that we have no leaks in or around the house. Our pump is submersible. Thank you very much.
Reply: Check for a leaky foot valve or check valve; check for leaks in well piping between the well bottom and the pressure tank
I'm not sure what "valve" you were told was bad. Perhaps a foot valve or check valve? A bad check valve or foot valve can lead to loss of pump prime and thus loss of water pressure. While that cause and symptom are not usually intermittent but rather a hard failure, a slow leak in a check valve or foot valve could show on occasion up as intermittent water pressure loss.
That is, if water is being run frequently and the leaky valve is a slow leak, the pump may retain enough water to not lose prime (assuming we're talking about an above-ground well pump here). But when water is left off for a longer period and the slow leak has time to lose more water from the pump, piping, and even pressure tank, one could lose water pressure.
Question: My water stops for 3-4 minutes, then restarts; and we get silt in tubs
my water runs fine for a few minutest, then stops for 3 or4 minutes, then starts back up. runs a while, stops, etc. getting silt in tubs too. pipes rumble when water pump runs now. that's new too. any help? - Anon
Reply: Check for sediment clogging and blocking proper response of the pump pressure control switch
When the water flow stops, has your pump also stopped?
Question: how do I prime my well pump?
Reply: see WELL PUMP PRIMING PROCEDURE
Question: We are losing just our HOT Water pressure. Cold water pressure is fine. What might be wrong?
I have an identical problem and again it is only with the HOT WATER but no pressure valve in the equation. ....except the ones on the outside of the house on the main line from the street and I have no problem with the Cold pressure only the HOT WATER and it stops as u said when another fixture is turned on elsewhere....this in turn makes the dishwasher not work properly.... R. Lane
PS I did turn the cold water inlet cutoff valve all the way open that is leading into HOT water heater....
Reply: Look for an intermittent water flow blockage in the hot water system, including cold water inlet and the water heater tank dip tube
R Lane you have already checked a key control, the cold water inlet shutoff at your water heater.
or on occasion, hot water clogging at
- a tankless coil or at individual faucets or
Follow-up: R Lane
R. Lane: I think your last sentence is what is wrong, that what it is a SINGLE faucet and the Dishwasher is getting older and coincidently is going out. ...I do appreciate you taking time to help. ...Thanks Sir
R Lane, it would be unusual for water pressure for a single faucet to come and go but I can think of a few possible explanations that each need further investigation:
Follow up: R. Lane
You know you may have something there sir. ..Funny both the hot water at the kitchen faucet and the dishwasher right next to it are the only things affected...in these bad economic times we have dealt with by hand washing and if we slowly turn on the hot water at that faucet it will go to full flow so definitely a blockage somewhere. ..Again I sincerely I appreciate your help you are of sterling character to offer so generously offer your wisdom and I appreciate it
Question: well pump not pumping any water, recovers when shut off overnight
oops I didn't put my name. I was asking about our well not pumping any water. We shut off power to it over night and turned back on the next morning and it worked. Now the same thing has happened. I'm hoping it works in the morning. What can this be? Where should we start? Well is the only way we have to get water. City will not come out this far in the woods. It's a submersible pump. - Cindy Howard
Cindy usually when water pressure recovers over night the cause is a poor well flow rate - running out of water. There may be other more less common causes however. See WATER PRESSURE PROBLEM DIAGNOSIS TABLE for some troubleshooting suggestions.
Ours turned out to be a bad pressure tank. The bladder burst and we had to replace it. Works great now. - Cindy
Sometimes a burst bladder in a water pressure tank gives strange water pressure behavior - because sometimes water can flow into or out of the pressure tank while other times, when the bladder becomes stuck over the tank inlet/outlet, no water flows. Also such tanks can become waterlogged, leading to pump short cycling.
Question: We have a deep well with no yield. Could the water table be varying seasonally?
deep well .... no water coming out... have replaced with new pipe... made sure it was not clogged and not pulling up sand. is there such a thing as the water table in the dry season, dropping too low for the pump to draw? - Agatha Brooks
Reply from Sam Waite:
For Agatha Brooks
2. With your new water pipe insert one anti-siphon valve (a one-way flap valve) for every 60 or 100 feet of pipe. You must have at least one of these in the vertical pipe. This valve prevents water in surface pipes, from flowing back down into your well. One of these valves should be near the surface well pipe connection. Yes, anti-siphon valves can freeze in place rendering them useless.
Question: what is the relationship between water pressure, well flow, and weather?
Does warm weather play a factor in water pressure? Every summer our water pressure lowers in the months of July & August. Thank you - Kevin
Reply: seasonal drops in water table in an area can affect well yield or flow rate
There can indeed be relationship between warm weather and water "pressure" though I'd call it a relation between warm weather and reduced well flow rate, or less water delivered by some wells, that may appear in the building as reduced "pressure" depending on how some folks talk about water flow.
Question: Repeated losses of water pressure and tripping circuit breakers
We have lost water pressure on three occasions now. The first time, the septic breaker was flipped, and resetting this brought back water pressure. The second and third time the breaker was not flipped, just no water. Pressure needle below the pressure tank showed zero each time. Any suggestions on what to look for?
Reply: Check pump, pump wiring, pump control switches and relays
Turned out to be a pressure switch fouled with Iron/sediment. Repairman recommended installing a filter between the well and the pressure tank to keep this out of the plumbing. Thanks - Colt
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