Low Water Pressure Diagnostic FAQs

Problems with weak water pressure at some or all plumbing fixtures or water faucets / taps

Water pressure is weak only at the Cold Water Faucets

The water pressure at my faucets is really low when opened on cold water.

The pressure gauge indicates 50psi, and lowers when the faucets are open, but not below 35-40.

So, as far as I can see everything seems to be in order.

The house was inspected for a sell a couple months ago and no problem was noticed, but it has been empty since.
- On 2020-05-10 by Ash

by (mod) - Diagnostic Advice for Poor Cold Water Flow when Hot Water Flow is Fine

Ash

We know that you have normal system water pressure - ranging between 35 and 50 psi at the pressure tank and gauge.

And we know that water pressure is normal (good) at hot water taps.

When water pressure is weak only on cold and not hot faucets, then there is a clog or a valve partly closed or some similar blockage.

Examples of causes of poor Cold Water Flow when Hot Flow is OK

Poor Cold Flow at Some or All Fixtures: Valve Closed or Blocked:

First confirm that there are no partly-closed valves in the cold water piping lines.

Watch out: where gate type water valves are used and less often where stop valves are used, it's possible for the valve stem to break so that you think the valve is open while actually internally the valve remains closed. You'd only discover this by disassembling the valve.

Poor Cold Flow at Some Fixtures-Faucet Damage:

Poor cold water pressure at an individual sink, shower, or tub can be caused by a broken O-ring or a damaged cartridge inside the faucet .

In the broken cold water faucet O-ring case, the problem may be more-recent while if the issue was too-much solder pushed into a joint, that poor water flow would have been present ever since that pipe connection was made.

Poor Cold Water Flow Due to a Blocked or Kinked Water Line:

Because there will be a cold-water feed into your water heater (and you have good hot water pressure) we know that the blockage, partly-closed or defective valve, or a similar problem is "downstream" or past where the cold water line feeds into your water heater.

So start there and follow the cold water piping.

Your photo shows a ball valve at the water pressure tank, and that your water piping is plastic, perhaps white PEX tubing that we discuss and troubleshoot at PEX PIPING INFORMATION .

It would be unusual but possible for a poorly-installed plastic PEX water line to be physically bent too far so that it kinks, blocking cold water flow, so that's another thing to watch for.

Where copper piping was used, by poor workmanship that pushed too much solder into a cold water pipe joint.

Where iron piping is used, it's possible for rust, sediment, corrosion to block some piping sections or elbows more than others.

Poor Cold Water Flow Due to a Leak?

I'm guessing that the poor cold water pressure is not due to a cold water line leak or you'd have seen water leaking somewhere by now.

Avoid these "Weak cold water flow only" cause guesses I found from AI's answer to this question (June 2026)

Blocked faucet aerator? Nonsense! both hot and cold have to flow through the faucet and its aerator, so if that were the problem, both hot and cold flow would be weak at that fixture.

Blocked, defective, or mis-adjusted water pressure regulator? Usually Nonsense! The building water pressure regulator is installed where water enters the building or for private well systems, it's controlled at the water pump pressure control switch. Adjustments to either of those controls will affect both cold and hot water pressure together, never just cold water pressure only.

At WATER PRESSURE LOSS DIAGNOSIS & REPAIR we give detailed poor water pressure diagnosis and repair suggestions.  

Also see WATER PIPE CLOG DIAGNOSIS for help diagnosing clogs in water supply piping.

Dirt, Mud, Silt in Water Supply or Well Bore

Muddy water with black grit comes out of well

I have a well that we replaced the pump about 10-12 years ago, my problem was happening about once a year or so, you would turn on the water and all of a sudden it would become very very muddy looking, and there would also be black grit almost like charcoal, it would become so bad that you couldn't flush the toilet because it would clog up the valve in the toilet and i'd have to replace it.

Now this problem is happening like every couple months ? Once I let everything settle down for hours I return and use the cold water it runs off and becomes clear again, and we go on for months without a problem, do I have to have my well dug deeper to find a better water source or deeper, or do you believe I should think about the pump being replaced again?

when we did replace the pump the last time I checked it and it would not operate at all when we pulled it and hooked it up outside the well, but why am I getting all this muddy/rust/grit looking love from my pump could the pump be pumping this because of a lack of water or do things move in a drilled well and water discoloration can happen because of it? Any help would be greatly appreciated, Thanks! On 2016-12-10 by Bill

by (mod) -

Bill:

I would ask a local well installer/repair company to check the well and well casing for damage to the casing, low water level in the well, or the foot valve too close to the well bottom.

If the well casing is damaged that can let more dirt fall into the well bore - and is repairable by inserting a well sleeve.

See WELL CLEANING PROCEDURES 

If the problem is persistent in the water supply you'll need to install a high capacity sediment filter system on your water supply.

See FILTERS, WATER.

Also for larger water storage tanks and rooftop tanks see WATER TANK CLEANING CODES STANDARDS 

Is there a chemical I can drop into the well to get rid of clogging mud and dirt without pulling the pump?

Is there any chemical I could possibly drop, in the water, to clean the water sumo screen, from dirts, without bringing out the sumo pump from the ground. Coz my submersible pump, ain't pumping fluently. On 2021-05-04 by Mr Stones I

And what's the name of this chemical cleaner ? Thanks

by danjoefriedman (mod)

@Mr Stones,

There are methods for cleaning clogged well screens, foot valves, inlets; the method depends on the type of well as I'll outline below.

I don't know what a "sumo screen" and "sumo pump" are? Perhaps you can help me out.

If yours is a drilled well using a borehole and a foot valve or if your well uses a submersible pump that picks up water directly in the well, you will do best to pull up the well piping and foot-valve or well pump for cleaning or replacement.

If yours is a driven point or sand point well see DRIVEN POINT WELL RESTORATION
at
https://inspectapedia.com/water/Driven_Point_Well_Restoration.php

Watch out: unless you are trained in the procedure and follow well cleaning product instructions to the letter, don't dump caustic chemicals down into a drilled well, borehole, or dug well; the risk is that you contaminate your well water, making it unsafe to drink; it can be very difficult to flush caustic or toxic chemicals out of those wells.

There are well cleaning chemicals that are used in wells, most-often these

Mineral Acids: hydrochloric, muriatic, phosphoric and sulfamic acids. (Muriatic acid is hydrochloric acid at an 18 % concentration). These are dangerous chemicals.

Other acids, organic products, like acetic acid (vinegar) are also used to try to dissolve scale that can clog a pump or foot valve.

See details at WELL CLEANING PROCEDURES 

What's the best way to clean a well bore liner screen?

What is the best method to clean a bore liner screen On 2020-04-10 Kevin

by danjoefriedman (mod)

Kevin

The most-extensive discussion of well bore liner screen cleaning are in the petroleum industry - rather than in the well bore industry.

Typically a chemical cleaner is pumped to the well bottom to dissolve scale, then a mechanical brush may be used to loosen sediment. The combined chemical and particulate contaminants are then pumped out of the well. See details at WELL CLEANING PROCEDURES 

How do I fix slow water pump discharge and gray sediment in the water?

I had a small leak in the PVC pipes between the well-head and the pressure tank so I shut off the well and replaced the leaking pipes, re-pressurized the tank to 95 PSI and now have a very slow discharge rate.

I have a problem with grey sediment in the water due to the vein of coal down there but have a filter system up top.

Could that sediment have settled back into the pump and is the cause of my problems now? On 2015-03-21 by Kevin Hromas

by (mod) -

Kevin

By slow discharge rate I infer you mean that that the water delivery rate is slow I'd look first for a leaky connection at the area of repair.

And sediment can clog a pressure control switch or even water piping or a water filter if one is installed - all leading to weak water flow.

And the 95 psi tank pressure escapes me. I cannot understand what you are doing but

Watch out: that pressure is very high possibly very dangerous if it exceeds the tank's rated pressure. A burst water tank can injure or kill someone nearby and a burst tank bladder will mean the pressure tank will stop working.

Well Pump Won't Pump Above a Very Low Pressure

Why can't my well pump deliver more than 10 psi water pressure?

My private well pump has low water pressure. It is enough to keep the toilet filling when needed and to run the hose that comes off the well but says only 10 lbs of pressure.

We have replaced the well piping because it was the metal pipe and appeared to be close to the end of its life with lots of rust and actually broke when we went to lay it on the ground.

We also replaced the pressure gauge, the control switch and checked the wiring. It is a submersed pump and when we pulled and measured it was 198 feet deep with water approximately 100 foot down from ground.

With the pressure even directly off the tank not being very much and the house being slightly uphill from the pump and no evidence of any leaks from well to home (with the low 10 lbs and it only filling my toilet and water heater and pressure appears the same as at the well for both water heater and toilet and hose at well) I am lost on what to repair or replace next. On 2014-08-21 by Teresa Emerson

by (mod) - If the pump is unable to deliver more than 10 psi

Teresa,

If the pump is unable to deliver more than 10 psi I'd be looking for

- low voltage
- a damaged or clogged foot valve
- a damaged or clogged pump impeller assembly
- a leak in well piping

How do I fix poor water pressure for our lawn sprinkler systems, no water pressure tank is installed

I don't have a tank so the water comes out by the pump so the pump runs the entire time I use my sprinklers. The pump runs but doesn't seem to run as high as it usually sounds so my water doesn't keep coming out. Do I need a new pump? I replaced it 4 years ago. - Debbie 4/15/12

Reply:

Debbie, usually when we see a water pump system with no pressure tank installed, it's a special-purpose single-use system such as the lawn sprinkler system you are describing. In that case the presumption is that when the sprinklers are running the potential water flow rate through the system is greater than the gallons-per-minute capacity that the pump can deliver.

In that case, once we turn on the lawn sprinklers by opening a water control valve and then turn on the well pump, the pump will never "get ahead" of the water pressure or flow rate through the system, and it will just keep running indefinitely until you shut the whole system down.

If nothing has changed in your system, valves, controls, equipment, the problem could be any of several things including

• a leak in the water piping between the pump and the sprinkler system
• a leak in the sprinkler system piping
• a control valve partly closed
• a worn pump that simply can't deliver water pressure as high as when new - such as a damaged pump impeller
• if the water source is a well (as opposed to a pond or stream) and the well flow rate has deteriorated the pump may simply have less water available and may even be cavitating as water levels in the well drop too low. See WELL FLOW RATE - water quantity problems.

Frankly this design makes me nervous because I worry that if the system and its controls were not set up by an expert we could turn on a pump without providing a pressure control switch for it - risking an overpressure in the water piping and bursting a pipe or possibly injuring someone.