How to Diagnose Bad Water Pressure Due to Clogged Water Pipes

  • CLOGGED SUPPLY PIPES, DIAGNOSIS - CONTENTS: Guide to Diagnosing Bad Water Pressure due to clogged water supply piping in a building. How to find where water pipes are clogged and how to repair this problem. How to diagnose loss of water pressure or loss of water in a building
  • POST a QUESTION or READ FAQs about clogged water pipes and their effect on water pressure; how to repair or replace clogged water pipes for better water flow and pressure in a building.

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This article explains how to Diagnose and Cure Bad Water Pressure Due to Clogged Water Supply Pipes - how to diagnose the loss of water pressure and the need for a replacement water pressure tank and water pump.

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.

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How to diagnose clogged building water supply piping as a cause of bad water pressure

Clogged steel piping (C) Carson Dunlop Associates

Clogged water supply piping can cause poor water flow in a building. This can occur suddenly from debris clogging a delivery pipe, often at a turn or "elbow" in the piping, but that's not common.

[Click to enlarge any image]

If the building water supply piping is blocked usually this is a long-standing problem.

Examples of causes of poor water pressure due to blocked pipes include

  • Water pipes becoming clogged internally due to rust or mineral build-up (is your water hard? are the pipes iron?),
  • Poor installation of the supply piping (did the plumber push too much solder into a copper pipe joint during installation?

The sketch (above left), courtesy of Carson Dunlop Associates shows how galvanized steel water supply piping becomes clogged from rusting or mineral deposits.



and see MUNICIPAL WATER PRESSURE DIAGNOSIS or WELL WATER PRESSURE DIAGNOSIS where we describe the effects of clogged piping on water flow and offer remedies for this problem.

If only hot water pressure and flow are poor, also see CLOGGED SUPPLY PIPES, HOT WATER.

There are two useful diagnostic tricks to determine if building water piping is clogged:

  • First make sure you rule out simple problems like a clogged water filter (See WATER FILTERS, HOME USE) , a partly-closed main water valve, or problems with the water supply source itself. That diagnosis procedure starts

    Also be sure to rule out clogged faucet strainers, broken o-rings in faucets, and similar fixture-specific problems which we discuss at Poor water pressure just at certain plumbing fixtures.
  • If water pressure is good when you first open a faucet, but immediately falls off to a poor flow, then the system pressure is good but there is probably a constriction in the piping.

  • If water pressure is good at some fixtures but terrible at others then it's not a system problem, it's a problem at an individual fixture or at water supply piping feeding that fixture. For example, awful water pressure at one sink could simply be due to a clogged strainer at the faucet.

  • If water pressure is good in some areas of the building but poor at others at all fixtures and if this problem has always been present, there may be a blockage at just one water supply pipe or connection, such as at an elbow clogged by solder. We've diagnosed this problem the hard way by starting to cut open supply pipes downstream from the last point where we found good water pressure.

  • If you run out of water, or can't seem to get enough water fast enough out of a well, see WELL YIELD IMPROVEMENT

A main water supply pipe failure between the municipal water main in the street (or from a private well) and water supply pipes in the building the building, can occur, perhaps by leaking or by becoming clogged with rust or minerals so that water is not being delivered to the home at good pressure or not at all (if the water line has burst).

In cold climates, the water supply line may have frozen outside or even in the building at an un-heated location.

Reader Question: how do I improve water pressure at a higher building location?

Relationship between water pressure & building height (C) CarsonDunlop Associates used with permission InspectApedia.comEddie said:

I have a wr60 pressure tank near lake being fed by submersible pump. Settings are 40/60 and tank pressure is 38 psi. There is a second pressure tank approx 600 feet away up a hill in the house.

The air pressure in this tank is set at 38 psi. There is never any water entering this tank

The water pressure reading at this tank is 34 psi which I believe is the line loss from the 60 psi reading down at lake. Can the cause of no water in this tank because the air pressure is higher than water pressure . Can I lower air pressure to 32 psi.


Eddie you give horizontal distance but not vertical distance between the two tanks - that height is a factor to consider

. But if absolutely no water is entering the upper tank, other explanations include that water pressure is not high enough to lift water the height distance between the tanks or the tank is an internal bladder type and the bladder has stuck to itself.

Our illustration shown here and discussed in our article WATER PRESSURE BOOSTER PUMP shows that if incoming water pressure at ground level were at 60 psi, at a building plumbing fixture that is 30 feet higher the effective pressure would be around 47 psi.

Quoting from that article

For every one foot we push water up, we lose 0.434 psi. Another way of saying this is that it takes one psi to move water up 2.31 feet.


Continue reading at CLOGGED SUPPLY PIPES, REPAIR or select a topic from the More Reading links shown below.

Or see PEX BRASS CONNECTOR LEAKS where we discuss corrosion build-up in brass elbows & tees that can clog PEX piping systems.

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CLOGGED SUPPLY PIPES, DIAGNOSIS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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