Low Water Pressure in Home (Diagnosing Problems, Solutions)

September 9, 2009 | by Fred (email) |

Low water pressure is a real downer. There’s nothing quite like looking forward to a hot shower and finding out that instead of 20 minutes of relaxation, you’ll spend 10 miserable minutes trying to squeeze yourself up against the wall under a dribbling shower head (tell us you haven’t been there at some point!)

Fortunately, low water pressure can be boiled down (no pun intended) to a few causes that are relatively easy to diagnose. You may have to call in a professional plumber to deal with some of these and even to pinpoint a diagnosis, but rest assured that they are repairable with a little perseverance.

Note that this article deals primarily with pressure issues associated with water connected to a public water supply.  While the same concepts also apply to well systems, there are more issues with well systems that can create pressure problems that I don’t cover here.

Reasons for Low Water Pressure

To identify the cause (and solution) for low water pressure, determine which type of problem best describes your situation.

Low Water Pressure At a Faucet or Shower Head

If the low water pressure is isloated to a single faucet or shower head, the most likely culprit is a clogged filter or aerator screen in the faucet itself. This is particularly common in shower heads, almost all of which are designed to be disassembled and cleaned periodically.  This can happen immediately after you have new plumbing installed too, since bits of solder or other contaminates may be stuck behind the screen from when the plumber (or you) soldered the pipes together in the first place.  This video on fixing shower water pressure is a good place to start if this is your issue.

Other causes for low water pressure in this scenario that are less likely:

• The valve controlling that branch of the plumbing is partially closed, or potentially stuck or clogged.  You can replace the valve to solve this problem.
• There’s something constricting the flow of water in the plumbing somewhere else (this will likely require a professional to snake the lines).
• There’s a bad crimp in the piping somewhere… Uncommon but it can happen, especially on <= 1/4 inch pipe runs to things like refrigerators.
• The plumbing is too small for the branch (e.g., a 1/4 run is used where a 1/2″ run is appropriate).

Lower Water Pressure on the Second Floor

Low water pressure on the second floor in almost always caused by a general lack of water pressure in the whole house that is exacerbated on the second floor.  Or, it can also be isolated to the second floor because there is a problem only with the second floor plumbing.  Here’s some things to check:

• Ask a neighbor if their pressure is low.  If a neighbor has low water pressure too, the issue is probably with the municipality.  You have a few options in this case: (1) contact the county/city and get them to fix it; (2) install a pressure booster system on the main line (requires a professional plumber);  (3) run a larger main pipe from the water main to the house (and larger plumbing throughout … very expensive solution but it can work… this would be a last resort).
• Check the first floor water pressure.  Is it low?  If so, the problem is systematic to the whole house.  Either there’s a major leak, or the water flow is being blocked.  Pressure regulators are known to clog eventually, and can produce this effect throughout the whole house.  If you have a situation where the water pressure briefly “spikes” when you turn on the water, and then goes to a dribble or much less, this is almost certainly a water flow constriction somewhere in the pipes or a valve.  If there is no spike in pressure, the problem is either a leak or low pressure from the public supply.

Low Pressure When Other Faucets Are On

If the pressure is low only when other faucets are on, there’s three likely culprits:

• A blockage in the pipes or a valve.  You will likely notice a “spike” in water pressure when the first faucet is turned on, quickly diminishing after that.
• A leak.  Find it and replace the pipe / patch the hole.
• Insufficient flow to the house.  Install a larger water main to correct this, or contact the public water supplier and ask them to check the system.

Low Water Pressure in a Neighborhood

If the entire neighborhood suffers from low water pressure, one of two things are true:

1. The main water supply to the neighborhood is insufficient.
2. There’s a systematic problem with the neighborhood’s plumbing.  For instance, some neighborhoods built in the late 80s have Polybutelyne plumbing, which can eventually crack or explode.  There could be multiple homes with leaks, thus lowering the water pressure for the whole neighborhood.

Small drops in pressure are normal in neighborhoods, particularly at high water use times (6-9am, 4-7pm).  You may have trouble getting the county/city to correct the problem if the issues are intermittant.  If the problem is bad enough, consider asking the HOA to address it with the county, or contact an attorney and discuss your options.

When to Contact a Plumbing Contractor

At the end of the day, if you’ve exhausted all other options, it’s time to get a plumbing contractor.  Many times they’ll be able to pinpoint a problem you hadn’t suspected was an issue.  Look for a reputable contractor, if possible one who has experience with homes in your neighborhood.  There may have been a systematic problem with the plumbing in all of the houses around you, and they’ll be the best qualified to address the situation.

(photo credit: Steven de Polo)