If your new faucet has low water pressure, the cause is rarely a defective faucet. In most cases, the problem is debris flushed into the aerator during installation, a supply valve that was not fully reopened, a kinked or undersized supply line, protective packaging left inside the spray head, or a flow restrictor doing exactly what it was designed to do. All of these are quick to diagnose and cheap to fix, usually with nothing more than a cleaning or a small replacement part. Before assuming the faucet itself is the problem, work through the checks below in order.
Start With the Aerator
The aerator is the small screened fitting at the tip of the spout, and it is the number one cause of weak flow in newly installed faucets.
Here is why: any time supply lines are disconnected and reconnected, small amounts of debris, pipe scale, sediment, and bits of plumber’s tape get knocked loose inside the lines. When water flows again, all of it travels straight to the first screen it meets, which is your brand-new aerator.
Unscrew the aerator by hand or with pliers wrapped in a cloth, and check the screen. If you find grit, rinse it clean, reassemble, and test. If the screen is damaged or heavily clogged with mineral scale, replacement aerators are inexpensive and available in standard sizes. This same buildup causes trouble on older fixtures too, and it is one of the [common faucet issues] worth checking any time flow weakens.
Prevention tip for next time: after connecting a new faucet, remove the aerator first, run the water for thirty seconds to flush the lines, then install the aerator. This one habit prevents most new-faucet pressure complaints.
Check the Shut-Off Valves
It sounds too simple, but partially open shut-off valves are behind a surprising share of low-pressure complaints. During installation, the valves under the sink get closed, and in the process of finishing the job, it is easy to reopen them only partway.
Reach under the sink and turn both the hot and cold valves fully counterclockwise. If a valve feels stiff, gritty, or will not open fully, the valve itself may be failing internally. Older multi-turn valves are especially prone to this, and their internal washers can degrade and restrict flow even when the handle says open. Swapping in a modern quarter-turn valve is an inexpensive, permanent fix.
Inspect the Supply Lines
Flexible braided supply lines are forgiving, but they have limits.
Kinks. If a line was bent sharply to fit the cabinet, the inner tube can crimp and choke flow. Look along each line for tight bends or twists and reroute them with gentle curves.
Undersized lines. Supply lines come in different diameters. A line that is too narrow for the fixture will feed it less water than it wants. Confirm the lines match the connection size your faucet specifies.
Old lines reused. If the original supply lines were reused during the install, mineral buildup inside them may be restricting flow. Lines are cheap; when a faucet is replaced, the lines should be too.
Look for Leftover Packaging and Plugs
Manufacturers ship faucets with protective plugs, stickers, and inserts in places you would not expect: inside the spray head, in the hose connection, or seated in the spout. A small plastic disc left in a pull-down hose connection can cut flow dramatically while still letting some water through, which makes it a confusing problem to chase.
Disconnect the spray head from its hose and inspect both ends. Check the hose connection under the sink as well. This takes two minutes and solves more new-faucet mysteries than most people expect.
Understand the Flow Restrictor
Sometimes nothing is wrong at all. Modern faucets include flow restrictors to meet water efficiency standards, and if you replaced an older, higher-flow faucet, the new one may simply deliver less water by design.
This is not a defect, and there is a real upside: efficient fixtures meaningfully cut water use over their lifetime. If you chose the faucet partly for efficiency, our guide to low flow faucets explains what the flow ratings mean and what to expect from them. If the restricted flow genuinely does not suit your needs, the better answer is choosing a model with a flow rate that matches your expectations, not fighting the fixture you have.
Rule Out the Cartridge
If the aerator is clean, the valves are open, the lines are clear, and there is no packaging hiding in the works, the faucet’s cartridge deserves a look. Debris from installation can lodge inside the cartridge itself, and occasionally a cartridge is faulty out of the box.
Remove the cartridge following the manufacturer’s instructions, inspect it for trapped grit, rinse, and reinstall. If flow is still weak and only this fixture is affected, a replacement cartridge matched to your faucet’s model number typically resolves it.
One Faucet or the Whole House?
A final diagnostic question worth asking: is the low pressure isolated to the new faucet, or do other fixtures share it? If it is only the new faucet, the cause is in the list above. If pressure is weak throughout the house, the issue lies beyond any single fixture, and that is the point where a licensed plumber should assess the system.
FAQs
Why is my brand-new faucet’s water pressure so low?
The most common cause is debris from the supply lines clogging the aerator during installation. Other frequent culprits are partially open shut-off valves, kinked supply lines, leftover packaging inside the spray head, and the faucet’s built-in flow restrictor. A defective faucet is rarely the reason.
How do I clean a faucet aerator?
Unscrew the aerator from the spout tip, rinse the screen under running water, and soak it in white vinegar if mineral scale is present. Reassemble and test. If the screen is damaged or badly scaled, replace the aerator with a matching size.
Should I remove the flow restrictor from my faucet?
No, removing it is not recommended. The restrictor keeps the faucet compliant with water efficiency standards and controls splashing at the designed flow rate. If the flow rate genuinely does not meet your needs, choosing a faucet model with a higher rated flow is the better solution.
Why is only the hot water pressure low on my new faucet?
When only one temperature is weak, the cause is on that side specifically: a partially open hot water shut-off valve, a kinked hot supply line, or debris concentrated in that line. Check the hot side’s valve and line first.
Do supply lines affect water pressure?
Yes. Kinked, undersized, or internally scaled supply lines all restrict the water reaching the faucet. Replacing old or damaged lines with properly sized new ones is an inexpensive fix that often restores full flow.
Get the Right Parts the First Time
Most low-pressure fixes come down to one small, inexpensive part, and getting the right one on the first trip is the whole game. Bring your faucet’s model number, the old aerator, or even a photo of the problem to Chatham Plumbing, and the team will match you with the correct aerator, cartridge, valve, or supply line so you’re not guessing at sizes. The showroom also carries a full range of faucets if you decide the fixture itself isn’t the right fit for your needs. Should the diagnosis point to something bigger than the fixture, they can recommend trusted local plumbers serving Chatham, Sarnia, and Leamington.