Why does my new faucet have low water pressure?
Usually one of four things: a shutoff valve under the sink left partly closed, grit knocked loose during the install now caught in the aerator or an in-line filter, a kinked supply line, or a faucet simply built for a lower flow than the old one. Check the valves, then clean the aerator. If only hot or only cold is weak, look at that side's valve, line and the cartridge.
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By Kasra Taheri, Founder, LoclisPublished
Researched and drafted with AI, then checked claim by claim against the sources listed below before it was published. Prices and rules change; the dates beside each source say when it was last checked.
Step by step
Read when to stop and call a pro, further down this page, before you start.
Step 1: Open both shutoffs fully
Check that the hot and cold shutoff valves under the sink are turned all the way open, the first thing Moen says to check.[1]
Step 2: Compare hot and cold
Run hot alone, then cold alone, and note whether one side is weak or both are.
Step 3: Clean the aerator
Unscrew the aerator from the end of the spout, rinse out any debris, put it back and test; replace it if the flow is still low.[1]
Step 4: Test without the aerator
With the aerator off and a cup over the drain, run the water briefly; strong flow means the aerator was the problem.
Step 5: Look at the supply lines
Follow each flexible line from valve to faucet and straighten any kink or sharp bend. To replace a line that is too short and stretched, close both shutoff valves first.
Step 6: Clean the in-line filters
If your faucet has filters in its supply lines, shut the water off, open the brass fitting, rinse the screen and reassemble.[1]
Step 7: Check a pull-down sprayer
On a pull-down or pullout kitchen faucet, rinse the screen washer between the hose and the spray wand.[4]
Step 8: Check the rest of the house
Run another sink and a shower; if they are weak too, the problem is not the new faucet.
Low pressure from a brand-new faucet is usually something small near the faucet rather than a problem with your plumbing. The usual suspects are a shutoff valve under the sink that is not fully open, grit caught in the aerator or a filter screen, a kinked supply line, or a faucet that is simply designed to flow less than the one it replaced. Start with the quick checks, the valves and the aerator, and many cases are solved in minutes.
Start with the shutoff valves
Moen's first check for any low-flow faucet: "As a starting point to troubleshooting low flow, it is recommended to always check that the water supply shut off valves under the sink have not been turned off."[1] After an install, it is easy to open them only partway. Turn each handle fully open.
Older valves can make this harder than it sounds. Multi-turn valves have a handle that tightens to force a rubber gasket onto a seat in the valve's middle,[8] and after years in one position that gasket or the stem can stick or leave the valve partly closed even when the handle is turned all the way.
Clean the aerator
The aerator is the screen at the tip of the spout, and it catches everything that comes down the line. Moen says: "Over time, aerators can accumulate debris and mineral deposits, which can restrict water pressure or distort the spray pattern."[3] Installing a faucet often shakes loose bits of scale and old pipe-dope from the valves and lines, and they land in that screen within the first few uses.
Moen's test is to remove the aerator, clear any debris, put it back and try the water again, and to replace the aerator if the problem persists.[1] Lay a towel or the drain stopper in the sink first so the small parts do not go down the drain.
Some faucets have no aerator you can reach, and on some Moen models of that kind, filters at the end of each supply line do the same job and are cleaned the same way.[3] On some models, filters sit in the brass ends of the hot and cold supply lines and are reached by unthreading the fitting with a wrench, rinsing the screen and reassembling.[1] Shut the water off first.
If only hot or only cold is weak
A one-sided problem narrows things down. Check that side's shutoff, its supply line and any filter on that side. When only the hot or only the cold runs weak, Moen's fix for its own bathroom faucets is a new cartridge or a clean in-line filter.[1]
Kitchen sprayers and side sprays
Pull-down and pullout faucets have one more screen. Moen describes a screen washer between the hose and the spray wand, and notes that with the screen washer out, water running through the hose should be fairly strong; if there is little or no water, there may be an obstruction further back in the system.[4]
On a faucet with a separate side spray, the diverter sends water to one or the other. Moen's guidance: "If there is a shared flow between the spout and side spray or if only the side spray is getting good flow, replace the diverter."[2]
Kinked or wrong-length supply lines
Supply lines must be installed correctly to avoid issues such as low water pressure and leaks.[8] A flexible line pushed into a tight cabinet can fold flat, and a line that is too short gets stretched at a sharp angle. When buying lines, measure the distance from the supply stub-out to the fixture's water inlet and add a few extra inches.[8]
The faucet may simply flow less
New faucets are often built for lower flow than the ones they replace. Moen makes all of its bathroom sink faucets at 1.2 gallons per minute, its kitchen faucets with or without a side spray at 2.0 gallons per minute, and its pullout and pulldown kitchen faucets at about 1.5 gallons per minute.[1][2] Federal rules cap lavatory and kitchen faucets made after January 1, 1994 at 2.2 gallons per minute, measured at a flowing pressure of 60 pounds per square inch.[6] WaterSense labeled bathroom faucets use a maximum of 1.5 gallons per minute, and WaterSense also set a minimum flow so labeled faucets perform in homes with low water pressure.[7]
On adjustments, Moen says: "All manufacturers must adhere to these standards and no adjustments can be made."[5] When a faucet delivers less than its rated flow, Moen points to low water pressure, a blockage in the plumbing or in the faucet, or a faucet malfunction.[5]
When it is not the faucet
If the shower and other sinks are weak too, the new faucet is not the cause. In older homes with hard water, scale inside the pipes can be the reason; Virginia Cooperative Extension notes: "In pipes, excessive mineral scaling can reduce water flow and pressure."[9] Our guide to keeping faucets and showerheads free of mineral buildup covers testing for hardness.
Stop and call a pro if
- A shutoff valve will not open fully, or leaks at the stem when you turn it.
- The whole house has low pressure, or it dropped suddenly in several places at once.
- Flow is weak even with the supply line disconnected and held over a bucket, which points to the valve or the pipe behind it.
- You see water under the sink, at a connection or in the cabinet floor; see fixing a leaking pipe under a sink.
- The pipes are old galvanized steel and pressure has been falling for years.
Getting help on Loclis
Licensed plumbers on Loclis can find the cause and quote the fix. You can look up plumbers in Blacksburg, browse low water pressure repairs, read about replacing your own fixtures, or see every plumbing answer.
If the pressure is still low, describe the low water pressure once and licensed local plumbers quote it.
Common questions
- Can I remove the flow restrictor to get more pressure?
- Moen says flow rates are set by federal standards that all manufacturers must follow and that no adjustment can be made. If the faucet runs far below its rated flow, look for a blockage instead.
- Why was my old faucet stronger?
- It may simply have been built to an older or higher flow. Moen makes its bathroom sink faucets at 1.2 gallons per minute, below the 2.2 gallon federal cap. A lower-flow faucet fills a basin more slowly but uses less water and less hot water.
- Only the hot water is weak. Is that the water heater?
- Start at the faucet. Check that the hot shutoff is fully open, that the hot supply line is not kinked, and that any in-line filter on the hot side is clean. If the hot is weak at every tap in the house, the problem is upstream of the faucet.
- How do I get a stuck aerator off?
- Wrap the aerator in a cloth and turn it gently with pliers so the finish is not scratched. Some aerators are concealed inside the spout and need the small key that came with the faucet. If it will not move, a replacement aerator costs less than a damaged spout.
- Does a new faucet need flushing?
- Running the water for a minute with the aerator off, catching it in a cup over the drain, clears loose debris before it lodges in the screens. It is a good habit after any plumbing work that disturbed the lines.
Sources
- [1] Bathroom Faucet: Low Flow, Moen. Checked October 26, 2026.
- [2] Kitchen Faucet: Low Flow, Moen. Checked October 26, 2026.
- [3] Faucet Aerator Cleaning, Moen. Checked October 26, 2026.
- [4] Cleaning and Installing Screen Washers, Moen. Checked October 26, 2026.
- [5] Is there an adjustment that I can make to my faucet to increase the flow of the water?, Moen. Checked October 26, 2026.
- [6] 10 CFR 430.32 Energy and water conservation standards and their compliance dates, Electronic Code of Federal Regulations, U.S. Department of Energy. Checked October 26, 2026.
- [7] WaterSense: Bathroom Faucets, U.S. Environmental Protection Agency. Checked October 26, 2026.
- [8] Oatey 101: Stops and Supply Lines, Oatey. Checked October 26, 2026.
- [9] Virginia Household Water Quality Program: Hardness in Household Water (442-664), Virginia Cooperative Extension, Virginia Tech. Checked October 26, 2026.
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