How To Fix Low Water Pressure After Installing A Water Filter


Water pressure can drop after installing a water filter. A tube kink, partially-open valves, low feed pressure, trapped air and poor water quality are the most common causes of low water pressure after installing a water filter.

If you have recently installed an efficient water filtration system to improve your water quality, but it’s taking ages to fill up a water pitcher there may be a problem with the water flow or water pressure.

Experiencing a pressure drop can be annoying because you paid to upgrade your lifestyle and the filter seems to be doing the opposite. Check out our list below of all the problems that can cause a pressure drop, and how to fix them.

  • Water filters slightly restrict the flow of water to remove contaminants and improve the quality of the water.
  • Valves that are closed or only partially open, kinked water lines, clogged filters and trapped air are the most common cause of low water pressure after installing a water filter.
  • An optimally functioning water filter should not cause a substantial drop in water pressure.

Types of water filters that can affect water pressure

Studies reveal that 63% of US citizens are exposed to unsafe drinking water. Investing in a quality water filter has become almost a necessity. However, once you hit the market, you’ll be overwhelmed by the number of choices.

There are several different types of water filters that once installed can affect your water pressure. The most common ones are:

  • Whole House Water Filtration Systems: Whole house water filtration systems are point-of-entry units that purify every drop of water in your home. They feature multiple filtration layers to make water sediment-free. A quality whole-house filter removes chemicals like chlorine, iron, and other heavy metals. The filter also targets volatile organic compounds and pathogens like bacteria if its filtration stage features a UV stage.
  • Under-sink filters: Under-sink filters are installed below your sink directly into the water line. They are compact and lightweight models that offer a continuous supply of purified water for cooking and drinking purposes. Many homeowners prefer under-sink filters due to their affordability and ease of installation. They are also pretty easy to maintain, and most can last for up to 10 years with minimal maintenance.
  • Reverse Osmosis: RO systems are the most effective in removing contaminants, metals, chemicals, and parasites from your drinking water. They feature a semipermeable membrane that allows water to pass through.

Reasons Why Your Water Pressure Is Low After Installing a Water Filter

Are you unsure why your water pressure has dropped down to a trickle after installing a water filter? Here are all the reasons why, and the common fixes to help you out.

1. Closed Or Partially Opened Valves

Depending on your water filtration system you will have either one or several valves.

The most widely used valves are pressure-limiting valves, saddle valves, diverter valves and exit valves. Under-sink filters, reverse osmosis systems and whole house systems all have valves.

If any of these valves are only partially opened (or incorrectly installed), your water pressure will be reduced.

Fix It

Check each of the valves attached to your filtration system. Make sure they are open all the way (to the maximum capacity) and see if the pressure improves.

Turning the valve all the way to the left should open it fully.

2. Trapped air

When installing a water filter, air can easily enter your water lines or pipes.

Trapped air affects the water flow through your plumbing system, and reduced the water pressure and changing the flow rate at the tap.

If you’ve noticed that the water flow rate or pressure has been changing, or is different between faucets (e.g. bathroom vs kitchen) air may be stuck in your plumbing system.

Fix It

The steps to remove trapped air will depend on your system.

If you have a whole house system:

  1. Turn off the Main Water Supply Valve
  2. Turn on every faucet and appliance connected to the water supply (including your washer and dishwasher). 
  3. Open both hot and cold faucets. You don’t need to open the faucets at full force; you can open them halfway.
  4. Flush the water out of your toilets
  5. Turn the main water valve back on
  6. Let the water flow through your faucets for another few minutes (5 minutes is usually enough). There should be a steady flow of water out of each faucet.
  7. Begin to turn off the faucets, starting with the one farthest from the main valve and move towards the ones closest to the main. 

If you have a point-of-use system (e.g., RO, under-sink)

  1. Close the valve that controls the feed water. This will stop any new water entering the system.
  2. Open the faucet that is connected to the filtration system.
  3. Allow water to run for 5 minutes, or until the flow of water stops if the storage tank has been exhausted (on RO systems).
  4. Reopen the feed water valve.
  5. And allow water to continue to flow through the tap.
  6. The flow should be steady.
  7. Turn the tap off.

If you are not sure if trapped air is your problem, Water Purification Guide has details on all the signs to looks out for available here.

3. Clogged Filter

A clogged filter has a negative effect on water pressure. The clogged pores of the filter slow and prevent the water from passing through.

A filter does not need to be old to become clogged. New filters can become clogged with debris from a new filtration system. Which is why it’s important to always a flush a new system, and look out for any loose material when installing it.

If you have had the water filter in place for a while, when was the last time you replaced your water filter cartridge? The key to optimal water pressure and filter operation is replacing cartridges regularly.

Even if you change your filter at the recommended time, you can still have a clogged filter because of high sediment loads in your water or from high water usage.

This is especially true for days when you use more water for drinking or cooking.

Fix It

Replace the filter cartridge as soon as possible to enjoy high water flow and good water pressure.

Depending on your filtration system you may need to flush the filter cartridge before installing it.

A few filtration systems also feature a filter light indicator to let you know when to replace your water filter. However, not all filters have one. So, make sure you check the product manual to know when to change your filter.

4. Poor water quality

Water high in contaminants, especially sediment (think dirt), can lower the water pressure. Lots of sediment in your water (and other contaminants) can make your water ‘thick’ and clog your filters.

Even if you previously had very little impurities in your water, water quality can change. Especially during storm season, or regular wet weather.

So, if your tap or well water has a higher amount of minerals, metals, or sediment, it’ll overwork the filtration system. As a result, you’ll encounter slow filtration and a drop in pressure.

Fix It

Changing your filters more often than what is recommended is an easy way to stop your water quality impacting the pressure of the water.

A good way to know when to change your filters is by using a TDS or TSS meter. These meters measure how much dissolved or suspended solids are in your water. As the quality of your filter declines the amount of these solids in your drinking water will increase. A TDS more than 100 mg/L is considered high.

Installing a sediment pre-filter can also help improve water pressure. These filters prevent your main filters from clogging by removing contaminants before they reach your water filtration system

Because you cannot stop the contaminants from existing, a more expensive option is to switch to a more extensive filtration system to upgrade your water quality and get optimal water pressure.

5. Flow water pressure

High incoming water pressure is ideal for better water flow through and from a filtration system.

Your home water pressure must be between 40-60 psi. Anything lower than that would negatively affect the water pressure flow.

The pressure of your water may not be something you noticed before installing the water filter, but can quickly become apparent.

On a side note, if you encounter this issue only from the unit’s faucet, your filtration system is to blame, not the incoming water pressure. A few filter systems restrict the pressure because they cannot work at high pressures, and is why you may experience a slow water flow rate.

Fix It

Inquire about the pressure changes from your local water supplier. If the issue is isolated to your property, the water utility can fix it by cleaning the dirt in the water distribution lines.

Otherwise, you may just need a water pressure booster pump. Installing one at the main water line will take care of the issue, or installing one directly to your filtration system – depending on the type of system you have.

If it’s a whole house system you may need to hire a professional to install the booster pump, but several are available online (e.g., Amazon.com) for smaller systems, like reverse osmosis units.

Water Purification Guide has more information on how to improve an RO system by using a booster pump, available here.

6. Kinks in water line

A loop or roll in the water line or tube can cause them to kink. This reduces the water pressure and limits the flow as you turn on the faucet.

Kinks can also lower the pressure of the water before it reaches the filtration system.

Fix It

Fixing a tube kink is relatively straightforward. You need to go over the line carefully to make sure there aren’t any sharp turns (kinks) affecting the water flow, and you’re good to go.

Kinks often happen when we move things around, especially under our kitchen sinks.

7. Blocked Aerator

Faucet aerators are meant to shape the stream of water flowing through the faucet and maintain the pressure flow.

However, like anything with small holes they can become clogged either during transport, installation or over time from mineral deposit accumulation. A clogged or blocked aerator stops the water from flowing properly and a severely clogged faucet aerator entirely restricts water flow.

This reduction in water flow results in lower water pressure.

Fix It

Take the faucet aerator apart and clean it. You can gently use a needle to push any stubborn debris out, but this may also damage the aerator.

Instead, you can dip it in vinegar overnight to loosen the dirt.

Afterwards, rinse it thoroughly with lukewarm water and scrub it with a brush to remove the remaining debris.

Place the aerator back on and check the water flow. 

If the aerator is damaged, or if the debris/dirt is stuck to the mesh you can buy a replacement.

8. Low Tank Pressure

You can encounter a pressure drop from low tank pressure if you own a reverse osmosis system (either a point-of-use unit or a whole house system).

Reverse Osmosis systems have a storage tank that stores clean water. Generally, it takes 2-4 hours for the tank to fill up. It’ll take around 5 minutes to fill a water glass without the tank.

The storage tanks of RO systems work via air pressure. However, the flow rate is severely affected when the pressure of the tank is low. An empty tank must have 5-8 psi of water pressure.

So, if your RO tank has low pressure, it’s the likely cause of your water pressure drop.

Fix It

Close the feed water valve to drain the tank water and empty it. Next, find the blue covering on the valve beside the RO tank. Check the air pressure using a pressure gauge.

If you spot low pressure, you can actually use a bicycle pump to provide the needed pressure. Ideally, adding pressure up to 8 psi will do.

However, a far easier option that doesn’t involve guess work is to buy a pressure valve and booster pump if needed. Also, simply making sure the tank is full before running the faucet can often fix this problem – especially if the RO has only just been installed.

Caution: Make sure you do not over-pressurize the tank. Otherwise, it’ll damage the air bladder.

Frequently Asked Questions

What PSI Should My Water Filter Be?

Your water filter should have a minimum of 40 psi pressure to function correctly. However, this varies depending on the type of water filtration system installed in your home.

Generally, experts recommend keeping the water filter psi between 40-60. However, RO systems, being powerful, are capable of handling higher water pressure than 60 psi.

You can always check your model’s instruction manual to learn about the optimal psi of your filtration system.

Do Water Filters Restrict Flow?

Water filters do restrict the flow of water due to filter media. However, this is to allow the filter to remove the contaminants and purify your water. The natural restriction of water flow from a water filter should not greatly reduced your water pressure.

While other reasons can contribute to a restricted water flow, from unopened valves to blocked aerators, your water filter may provide restricted flow even when working optimally. This generally happens due to the filter media that traps the unwanted contaminants.

If the water flows quickly from the filter media, it implies its compromised filtration process. So, for it to become contaminant-free, it must pass slowly from the media, and you’ll naturally experience a restricted flow as a result. However, it doesn’t indicate the water pressure will be low – it just won’t be excessive.

Why Does My Water Filter Get Dirty Quickly?

If your water filter gets dirty quickly, it indicates heavily contaminated home water. High levels of sediments and chemicals in the water degrade and clog the filter quickly, decreasing its lifetime.

If you’ve recently had construction-related work, it might have led to additional sediment or contaminants entering your tap or well water. Consider removing the filter and flushing it. Generally, this should fix the problem. However, if it doesn’t work, perhaps you’re dealing with heavily contaminated water.

You cannot do much to reduce the water contaminants in your water supply. However, replacing the filters timely can give access to purified water.

Theresa Orr

Theresa Orr is an Earth Scientist who specializes in determining past climates from rocks using geochemistry. Her passion for clean water drives her to breakdown the science to provide easy to understand information that everyone can read.

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