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How to Repair Bad Water Pressure Due to Clogged Water Pipes InspectAPedia®  -     How to Diagnose Bad Water Pressure due to clogged water supply piping in a building What does it mean if cold water pressure is good but hot water pressure is bad? Bad water pressure repair alternatives, which method to use

This article describes How to Cure Bad Water Pressure Due to Clogged Water Supply Pipes . The process of diagnosis and the costs of the repair are explained. Consumer advice on saving money on well repair costs includes a review of the parts and labor costs of a typical well pump and pressure tank replacement case.

Readers of this document should see See Clogged Piping / Tankless Coil & Hot Water Flow for a discussion of loss of water pressure due to clogged tankless coils and also see Diagnosing loss of water pressure or flow in a building.

© 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Guide to Repair of Clogged Water Supply Piping and Poor Water Pressure & Flow

The reduction in pipe diameter means a corresponding reduction in the flow rate seen at building plumbing fixtures. When you first turn on a faucet water pressure may be normal or "high" but as soon as water starts to flow the pressure and flow fall off to a noticeably lower level. This is the classic diagnosis of clogged water piping. But we don't know, yet, how extensive the clogging is - a single elbow, a clogged faucet strainer, or an entire length of clogged water piping can all produce this effect.

The suggestions which follow presume you’ve already followed our diagnostic suggestions to get an idea of the type of water supply flow problem that is present.

That’s important because some water pressure problems are due to water flow problems caused by a water pump, water pump pressure control, water tank, and on municipal water supply systems, flow problems may be due to problems with the water pressure regulator, water supply piping from a municipal supply, or even water meter and main water valve problems.

Here we discuss how to correct bad water pressure due to apparent clogs in water supply piping. First we need to do some further diagnosis to determine if the poor water flow problem is at every fixture in the building or just at some of them.

How to Correct Poor Water Pressure & Flow at One or More Plumbing Fixtures When Some Fixtures Flow Well

If poor flow is at just one fixture it’s a good bet that we can trace the flow problem to a local issue that we should be able to repair without more extensive plumbing surgery.

If you have good water pressure at some fixtures but not at others, you probably have a clog in building piping (such as due to mineral deposits, rust, or even excessive solder in new work), or mineral and debris clogged strainers at faucets and shower heads (check these first). Also see Water pipe clog diagnosis.

Slow water at the sink - check for debris or mineral clogging of the sink faucet strainer

If the slow fixture is a sink, first check the strainer – debris-clogged strainers can simply be un-screwed. If the pressure is suddenly wonderful you need a new or cleaned strainer, that’s all.

Slow water fill at a toilet - check or replace the toilet tank fill valve

If the slow fixture is a toilet, often the toilet tank fill valve itself becomes clogged with debris; it may be possible to remove, clean, and reinstall the valve but often it’s easier to just install a new one. We sometimes also find clogging at the small shutoff valve or water supply riser to the toilet.

Slow water flow at a shower - check for debris or mineral clogging in the shower head or flow restrictor

If the slow fixture is a shower head, debris or mineral clogging can be diagnosed by removing the shower head and, as with the sink strainer, look for good water flow. If we find that the problem was the shower head, just replace it. Some shower head models claim to be resistant to mineral clogging by using rubber or other flexible components to form the spray.

Bad plumbing valves or bad fixture supply risers: Plumbing valves or shutoff valves to individual fixtures or valves controlling sections of water supply piping can also become clogged with debris, minerals, or even a broken faucet washer.

How to Fix Bad Hot Water Pressure if Cold Pressure is OK

Poor hot water flow but good cold water flow at one or more plumbing fixtures usually diagnoses mineral clogging in the water heating system. Heat causes mineral precipitation out of hot flowing water faster than out of cold water, that’s why often mineral clogs appear on hot water components of a plumbing supply system first.

For a complete list of articles on diagnosing hot water problems See HOT WATER IMPROVEMENTS and HOT WATER QUANTITY IMPROVEMENT.

Guide to Improving Hot Water Pressure & Flow When Heated by a Tankless Coil

See these articles for diagnosing and improving hot water from a tankless coil:

TANKLESS COILS
  Clogged Piping / Tankless Coil & Hot Water Flow
  Mixing Valves
  Tankless Coil Leaks
  Tankless Coil Hot Water Increase

But beware, acid flushing a coil is not a permanent repair, and some plumbers will tell  you that the acid-etched pipe surface inside the tankless coil will clog more rapidly than before.

Install a water softener: If you find a pile of tankless coils like those in this photo during a building inspection you might suspect that this building has had a history of repeated clogging of tankless coils used for domestic hot water. After the tankless coil was flushed with acid, the building owner would have been better off installing a water softener to protect against subsequent mineral clogging of the tankless coil interior.

How else can we Improve the Hot Water Volume & Quantity When Water is Heated by a Tankless Coil?

See HOT WATER IMPROVEMENT for a detailed guide to improving hot water quantity and flow when a tankless coil is installed as well as using other methods of hot water heating

See Mixing Valves for details about mixing valves on boilers and tankless coil systems and for an explanation of how an anti-scald or tempering valve can increase the volume of hot water available from a tankless coil hot water system.

We discuss tankless coils in detail at Guide to Tankless Coils on Heating Boilers.

Guide to Improving Hot Water Flow When Piping Itself is Clogged

Building water pressure that is poor at all fixtures at the hot water tap, or at all fixtures at both hot and cold water taps may be due to clogged piping, which we discuss here. Other links at the end of this article provide guides for diagnosis and repair of other causes of bad water pressure throughout a building.

Use of acid flushing to clear tankless coils or building water piping

How to Fix Bad Water Pressure Throughout a Building or in Large Areas: all Hot Water, all Cold, Water Fixtures, or all Both Hot and Cold Fixtures have Bad Water Pressure & Flow

How to diagnose bad water pressure in the whole building or in large areas

Where an entire building or large building areas have bad water pressure, check to see if there is clogging at a valve, pipe section, or pipe elbow close to the water source. On occasion we’ve found that a building always had bad water pressure after a plumbing “repair” had been performed near the water tank. The installer had pushed too much solder into a pipe elbow, blocking water passage through that fitting. It was discovered by making successive cuts in the supply piping beginning back near the source to check for good water flow.

Clogged water filters cause bad water flow throughout a building and can cause water pump problems (if a private well system is installed. Water pump short cycling is discussed further at CAUSES OF SHORT CYCLING)

How to diagnose Bad water pressure in just some areas

Where a single or one or two plumbing fittings are causing poor water pressure, due to poor installation (solder blobs), damage (broken faucet washer or other debris clogging an elbow or valve), the fix is to find and replace the culprits.

Where long sections of piping have become mineral-clogged

1. Install a water softener but remember that clogged water supply piping that has not been repaired using an acid-flush will need to be replaced. Installing a water softener won't "un-clog" mineral-clogged water pipes. See WATER SOFTENERS to discuss problems with water hardness.
   
   
2. Install larger diameter water piping - this method will provide piping that will deliver adequate water flow and pressure for a longer time before clogging up due to high mineral content in the water supply. As you can see in the sketch above, courtesy of Carson Dunlop, increasing a pipe size from standard 1/2" to 3/4" in diameter more than doubles the water flow capacity in the piping!

We took this second approach on a building where we found that the hot water line clogged with a combination of minerals and iron. On cutting open the old hot water supply pipe we saw that its interior was blocked to a mere pinhole of remaining water passage.

But the cold water line was basically clear. So we replaced the hot water line, including straight runs and all elbows, with a ¾” copper pipe. The repair has continued to function well for nearly 30 years.  

Contact us know if you have other questions or repair ideas or if this material leaves you with a question or suggestion.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website

• HOT WATER IMPROVEMENT - how to get more domestic hot water from your water heating system
• How to Diagnose & Repair a Bad Water Pressure Due to Clogged Water Pipes to diagnose clogged supply pipes
• How to Repair Bad Water Pressure Due to Clogged Water Pipes to fix clogged water pipes
• Water Pump Problems? How to Diagnose & Repair Poor or No Water Pressure
• How to Know if the Right Repair Was Performed to Fix Lost Water Pressure
• Water pump and pressure tank repair diagnosis & cost

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

PLUMBING TOPICS
HOT WATER IMPROVEMENT
OIL TANKS
SEPTIC SYSTEMS
TANKLESS COILS
  Mixing Valves
  Tankless Coil Leaks
WATER PRESSURE REGULATOR ADJUST
WATER PRESSURE REPAIR GUIDE & COSTS
  Questions about lost water pressure
  Advice to a homeowner
  Adjusting Water Pump Pressure Control
  Right Repair to Pump & Tank?
  Well Pump & Tank Replacement Costs
WATER PRESSURE LOSS DIAGNOSIS GUIDE
WATER PRESSURE & FLOW MEASUREMENT
  Water Pressure Intermittent
  No Water Pressure
  Well Tank relation to Water Pressure
  Shaking the Water Tank?
  Water Pressure Tank Problems
  Water Pressure Tank Diagnosis
  Water pressure Later Returns "on its own"
  Water pipe clog diagnosis
  Water pipe clog repair guide
  Making the "right" repair
WATER PUMPS & WELL TANKS
WATER PUMP CONTROLS & SWITCHES
WATER PUMP TYPES & LIFE EXPECTANCY
WATER PUMP & TANK SAFETY
WATER SUPPLY & DRAIN PIPING
WATER TANK TYPES: WATER, OIL, EXPANSION, ALL
WATER TANK LIFE EXPECTANCY
WATER TANK REPAIRS
WATER TANK AIR, HOW TO ADD
WATER TANK BLADDERS & CAPTIVE AIR
WATER TANK REPLACEMENT
WATER TANK BLADDER PRESSURE ADJUSTMENT
WATER TANK PRESSURE CALCULATIONS
WATER TANK SIZE & VOLUME
WATER TANKS HOW THEY WORK
WATER TESTING
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL, PUMP, TANK LIFE EXPECTANCY

Technical Reviewers & References

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