5 Things You Need to Know About Buying a Water Heater Filter

The heating element of a water heater with scum and sediment

Water Heater Filter Systems: What is a water heater filter, how does it work, and the top things to keep in mind when picking a water heater filter system

A water heater filter protects your water heater, as well as your pipes, fixtures, plumbing connections, and water-using appliances that are supplied by your water heater. Hard water, sediment, and scale destroys traditional and tankless water heaters. These minerals and debris accumulate on the heating element which decreases heating efficiency and means your water heater will prematurely break down. Water heater filter systems should filter out sediment, and use a special blend to loosen existing scale and prevent scale from forming (anti-scale).

In this article, water heater filter expert Tony Special shares advice on the most important things to keep in mind when picking a water heater filter system. Tony has over 30 years experience producing water heater filter systems that are the most recommended in the industry by water heater manufacturers.

What is a water heater?

A water heater is an appliance that produces a continual supply of hot water at a preset temperature. They may also be called hot water heaters, hot water tanks, boilers, or heat exchangers. A hot water heater can be used in domestic and industrial applications to heat potable or non-potable water.

A hot water heater may have a tank or be tankless. As their names suggest, hot water tanks store hot water, and a tankless water heater produces hot water on-demand without storing water in a tank.

Hot water heaters with a tank use a reasonable amount of electricity or gas to preheat the water stored in their tanks. Such water heaters also use a rather large amount of energy to keep that water warm until it is used.

Tankless water heaters are more environmentally friendly because they use a lot less energy than hot water heaters with a tank. Tankless hot water heaters heat water when you need it (on-demand). Essentially, when you turn on the hot side of your faucet or plumbing fixture, the tankless water heater goes to work delivering hot water. If you switch to a tankless water heater you can save 21% and 43% on your water heating costs for the year.

5 Things You Need to Know About Buying a Water Heater Filter

“An effective water heater filter is essential for all water heaters. I can’t emphasize enough to people: whether you have a tankless water heater or one with a tank, you need a water filter if you have any water hardness or sediment in your incoming water. It’s just not worth risking your water heater.”

# 1: You need a water heater filter.

The first “given” about water heater filters is that if you have a water heater, you need a good filter for it. A good filter system and the replacement filters do not have to cost a lot, just ensure they are actually effective at addressing the problem at its core.

What is a water heater filter system?

The purpose of a water heater filter is to protect your water heater. Tankless water heaters and traditional water heater units are easily affected and damaged by scale and particulates in the water.

A good water heater filter system:

  • extends the life of your water heater
  • helps avoid additional maintenance and costly repairs or system replacement
  • ensures your water heater filter works as efficiently as possible
  • helps keep operating costs lower in the short and long-run

What are water heater filters used for?

A water heater filter protects your water heater. Unfiltered water contains minerals and particulate matter like sediment, dirt, or rust which can all clog your water heater, form a rock inside the heater, and reduce the efficiency until it finally dies. A water heater filter removes particulate matter and stops minerals that cause scale and corrosion from attaching to surfaces.

With a water heater filter, you can enjoy peace of mind that your water heater is protected from scale, corrosion, and particulate matter. This extends the life of your water heater itself, helps you avoid costly repairs or having to replace the whole water heater prematurely, and ensures your water heater is working as efficiently as possible.

How does a water heater filter work?

A water heater filter inhibits or stops scale. It does this by retaining hardness minerals so they don’t come out and scale up the heating elements or the bottom of a water heater. In a tankless water heater, scale inhibitor product protects scale from accumulating on all of the surfaces inside.

Siliphos scale control product is the best on the market – it has a two-fold approach to prevent scale and stop corrosion in water heaters. It works by forming a thin protective layer on the metal surface to inhibit the deposition of scale and corrosion on metal surfaces. It also helps loosen existing scale deposits. Be sure your water heater filter contain Siliphos scale control product.

A water heater filter should also remove and/or reduce debris from entering your water heater.

” A lot of so-called water heater filters do not actually “filter” the water. That’s really misleading, right? Such systems do not filter out particulates like sediment and dirt or take care of existing scale problems in your water filter; they just stop scale from forming in your water heater.

Definitely choose a water heater filter that removes particulate matter from the water, loosens any existing scale deposits, and stops scale from forming. You need to achieve these three things or what’s the point of your water heater filter? ” 

# 2: Make sure a water heater filter removes sediment / dirt / particulate, tackles existing scale deposits, and stops scale.

Not all water heater filters are created equal so ensure your water heater filter system accomplishes three very important things:

  1. Removes sediment, dirt, rust, and other particulate matter that is commonly found in an incoming water supply.
  2. Helps loosen existing scale deposits on your water heater. Ideally, a water heater filter should be installed simultaneously with a new water heater. If this isn’t the case, don’t worry too much but ensure you install a water heater filter ASAP. A filter that will help loosen the existing scale deposits is important.
  3. Stops scale from forming. Some anti-scale products work by forming a thin protective layer on the metal surface to inhibit the deposition of scale and corrosion on metal surfaces.

Be aware that many water heater filters do not remove sediment, dirt, rust, or other particulates in your water. Any “water heater filter” that does not remove (aka, filter) particulates should not be able to call itself a “filter” but unfortunately many manufacturers of water heater filters get away with it.

What causes scale in a water heater?

Hard water. Hard water contains minerals like calcium and magnesium, and a variety of other metals. These compounds are even more likely to come out in hot environments like a water heater. When water is heated, minerals and other compounds emerge rapidly and attach to the heating elements. Water heaters with scale deposits are less efficient because the scale absorbs the energy from the heating elements first before it heats your water supply. Scale also clogs the pathways of a water heater. Needless to say, scale destroys water heaters.

What causes sediment to build up in a water heater?

If your water supply has debris in it and you don’t have a filter, this debris will get into your water heater. Debris – sediment, dirt, rust, and other particulates – accumulates most significantly at the bottom of your water heater but can wind up in any orifice. Debris also damages all of your fixtures such as shower heads and toilets, and water using appliances like the dishwasher.

If you have a lot of debris in your water, it is highly recommended to have a point of entry filter (also called a whole house water filter) to capture the debris. A point of entry filter is installed in-line before a water heater filter and the water heater. If you have a point of entry filter, it’s still definitely recommended to have a water heater filter too because the water heater filter provides anti-scale protection and catches any remaining sediment (if the water heater filter is a finer micron than the whole house filter).

From time to time, you should turn your water supply off and drain the water heater to try to remove as much debris as possible. Water heaters have a drain at the bottom for this.

” When it comes to the water filter housing, there’s either stainless steel or plastic ones. Stainless steel is more durable and the “better” option, but they’re also more expensive; plastic housings – when made well – are perfectly fine too.

What’s most important is how the plastic water heater filter housing is manufactured: check if it made from a single mold – GOOD! –  or are the holes drilled after – BAD! “

# 3: A stainless steel housing is best. If you opt for a plastic housing, ensure it’s made from a single mold and that no holes were drilled separately.

Stainless steel water heater filter housings are superior to plastic ones. They are resilient to corrosive substances and chemicals, less likely to leak or burst, and have a longer system life overall. However, they do have a more expensive price tag.

If you are buying a water heater filter system with a plastic housing, determine if the plastic housing is manufactured from a single casting mold or if any holes are drilled after. (There are holes for the pressure release valve (if applicable) or holes for the bracket).

All holes should be present in the original, single casting mold. If holes are not done in the original casting, the filter head is weakened and could lead to leaks or even a burst. In some circumstances, if someone accidentally bumps or hits the system, it could loosen the threading and cause an instant leak. A ton of sellers drill or tap holes into the housing head themselves – stay clear of these housings.

Keep in mind that no matter the type of system, the less openings a filter head has, the less chance there is for leaks.

Bottom line: Ask the manufacturer if the housing is from a single mold casting, and if any holes were drilled after the original casting.

” A gauge on a home water heater filter system is gimmicky. It may seem like a useful feature and look good, but it’ll be inaccurate in this application and just isn’t needed. And whatever you do, especially don’t pay more to have a gauge. “

# 4: For home water heater filter systems, skip the water pressure gauge.

A water filter gauge is intended to measure a water pressure drop. Typically, when the pressure drops a lot it means it’s time to replace your water filter. However, gauges are inaccurate for relatively low volumes such as home water heater filter systems. Since not enough water is used or used consistently, it’s difficult to accurately measure a pressure drop. Therefore a gauge on a residential water heater filter system is virtually useless and will not accurately indicate when it’s time to change the filter. A water pressure gauge is fine for commercial or high volume applications that consistently use thousands of gallons of hot water per day – residential hot water usage is nowhere near this amount.

A gauge on a home water heater filter system may produce a false-positive or a false-negative reading. The pressure gauge might suggest it’s time to change the filter when the filter is actually fine. If you change the filter before it’s actually needed, that’s a waste and costs you extra money and time. Or, the gauge might miss when it is time to change your filter. This means your water heater is not receiving anti-scale protection or filtered water which can lead to costly damage and repairs.

To summarize, the here’s reasons NOT purchase a water heater filter system with a gauge:

  • The gauge is not an accurate indicator
  • Water heater filter systems with a gauge cost more (usually about $50)
  • A gauge on a water heater filter system is a gimmick, plain and simple.

When do you need to replace the water heater filter?

Most filters should be changed once per year. The calendar and/or a visual check is the best way to determine when to change the water filter on your water heater filter system.

You should check your water filter cartridge every 6 months or so by turning it upside down to see or hear the filter media rattling around. The Siliphos balls inside slowly dissolve as water passes through the filter. When all the material dissolves, the water heater filter needs replaced to fight against scale and corrosion. How much water goes through your filter and the water hardness impacts the filter life.

” Even though template assisted crystallization filters are effective at reducing scale, they come with some big drawbacks. TAC filters have low flow rates that can’t keep up with tankless water heaters. So unless you buy the huge systems – we’re talking 5 feet tall, over 100 pounds – they’re too big just to reduce scale and keep up with your hot water demands. Other technology is much more compact and economical.  Also, chlorine ruins TAC filters. If you’re on municipal water or have chlorine in your supply, you’ll need to remove the chlorine before it passes through the TAC filter. I hope you can start to see the point that template assisted crystallization just aren’t worth it in most situations when there’s far better options out here all things considered. “

# 5: Template Assisted Crystallization (TAC) filters have low flow rates that may not meet your hot water demands, chlorine ruins them, and it’s hard to know when to replace them.

Template assisted crystallization (TAC) may be a new term to some folks when it comes to water conditioning. Template assisted crystallization (TAC) transforms calcium ions into calcium crystals which are easily rinsed away by the water flow. Calcium crystals are stable and cannot attach to pipes, surfaces, hardware or heat exchanger components.

Sounds great so far, right? However, one major fault this style of water conditioning is that it is super sensitive to any chlorine in the water supply. Most municipal water supplies use chlorine in their water supply. If you don’t remove all chlorine before it enters a template assisted crystallization system, it’ll destroy the template assisted crystallization filter. Chlorine will use up all the template assisted crystallization media.

Template assisted crystallization filters have very low flow rates. The flow rates of TAC filters do not align with what tankless heaters are rated for and therefore your hot water flow rate will be drastically lower than what your water heater is rated for.

Another drawback of TAC water conditioning is that sellers provide very poor guidelines of when to replace a TAC filter. Sellers claim TAC filters last 2 – 5 years but you will not know when the TAC filter media is all gone. Template assisted crystallization media is contained deep within the filter – the media doesn’t rattle or give any indication it’s gone – and you’ll only know it’s gone by cutting open the filter and therefore ruining it.

If the template assisted crystallization filter media is gone, your water heater is not protected against scale and corrosion which can mean costly damage and repairs to your water heater.

Water Heater Filter Recommendations

Check out our full range of water heater filter systems and replacement cartridges.

Plastic housing: Premiere AMF-20S – 20″ Water Heater Filter System, 16 GPM flow rate

Big Blue tankless water heater filter system

Premium 20 inch water filter housing and AMF-SDR520 scale inhibitor cartridge. This system removes sediment and protects the heat exchanger in your tankless water heater from scale and corrosion to avoid failure. Ideal for large-capacity filtration needs, including high-flow and heavy-sediment applications.

Designed for all commercial and residential water heaters including Bosch, Navien, Noritz, Paloma, Raypak, Rheem, Rinnai, Stiebel Eltron, Takagi, and more.

Sturdy filter housing made from a single mold casting – it’s constructed with 15% more material. Heavy-duty, food grade plastic housing suitable for drinking water filters

5 micron deep grooved water filter cartridge with scale inhibitor to protect your heat exchanger and avoid tank failure. Rigid construction with 68 deep grooves. The grooved design increases surface area, extends the water filter cartridge life, and increases water filtration efficiency too! Siliphos ® scale control product prevents scale and stops corrosion. It works by forming a thin protective layer on the metal surface to inhibit the deposition of scale and corrosion. Helps loosen existing scale deposits too.

Built in pressure release valve (PRV), to release pressure before changing filters.

Stainless steel housing: Premiere SS210-TWH – 20″ Water Heater Filter System, 16 GPM flow rate

Stainless steel water filter - Tankless water heater filter model SS210-TWH with scale protection316L stainless steel housing is highly durable, resilient to corrosive substances and chemicals. Excellent 10 year warranty on housing. This system is not going to burst or fail like a plastic tankless water heater filter housing.

Includes AMF-SDR520 scale inhibitor cartridge. This filter is a premium 5 micron water filter cartridge with Siliphos ® scale control product prevents scale and stops corrosion. It works by forming a thin protective layer on the metal surface to inhibit the deposition of scale and corrosion on your tankless water heater.

The scale inhibitor cartridge has rigid construction with 68 deep grooves. The deep grooves increase surface area, enhance contaminant holding capacity, and promote fuller utilization of the depth-matrix for fewer cartridge change outs.

3/4″ or 1″ FPT connections that assist in maximum flow rate with minimum pressure drop

Unrestricted water flow of up to 16 gallons per minute which meets the water pressure demands of a tankless water heater. Drain opening at bottom of housing for easy flushing and cleaning.




5 Things You Need to Know About Buying a Water Heater Filter
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5 Things You Need to Know About Buying a Water Heater Filter
Residential and commercial water heaters are easily damaged by the sediment and scale in the water supply. A water filter is essential to protect your water heater.
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Premiere Sales
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