What is the difference between Type K and L copper?

Hey there! As a home improvement expert who has installed countless copper plumbing systems, I want to provide you with a detailed guide on Type K vs. Type L copper. I‘ll compare the key differences between these two popular varieties so you can decide which is best for your project.

Quick definitions

First, let‘s start with a quick refresher on what makes Type K and L copper unique:

Type K Copper

Also called "thick wall" copper
Wall thickness of 0.045 inches
Can withstand pressures up to 1,000 PSI
Approved for temperatures up to 800°F

Type L Copper

Also called "thin wall" copper
Wall thickness of 0.035 inches
Withstands pressures up to 700 PSI
Approved for temperatures up to 600°F

As you can see, Type K has thicker walls and can handle higher pressures and temperatures. But Type L is more malleable and easier to work with. Now let‘s look closer at how these copper types get used.

Popular uses for each type

When it comes to residential and commercial plumbing, Type K and L copper tend to get used in the following ways:

Type K uses:

Underground water service lines from the street to your home. Type K is durable enough to withstand being buried directly in the ground.
Interior water distribution lines carrying pressurized water throughout the home.
Natural gas piping, thanks to Type K‘s ability to withstand high pressures safely.
Drain, waste and vent (DWV) systems due to its corrosion resistance.
Air conditioning lines and refrigeration systems (in some cases). Type K can withstand the higher pressures.

Type L uses:

Hot and cold water lines supplying water to fixtures and appliances. This is the most common use for Type L.
Recirculating hot water loops to provide instant hot water at faucets.
Water heating systems like boilers and solar water heaters.
Smaller diameter water piping for things like laundry sinks or ice makers. Easier to bend Type L for tight spaces.

As you can see, Type K is typically used where it needs to withstand higher pressures, like natural gas lines. Type L is the go-to choice for indoor water delivery in most homes.

5 Key differences between Type K and L

Let‘s dive into the major factors that set these two copper varieties apart:

1. Durability

With walls that are 25% thicker, Type K copper is more rigid and durable. It holds its shape better and resists dents or punctures more than the thinner Type L. This makes it a better choice for high-pressure systems.

2. Flexibility

The thinner walls of Type L copper make it more malleable and easier to bend by hand or with light tube benders. Type K is more prone to kinking if bent too sharply. This flexibility makes Type L ideal for snaking pipe through tight spaces.

3. Cost

Type L copper pipe is generally 5-10% less expensive per linear foot compared to Type K. This cost savings comes from the thinner walls requiring less copper material. For large plumbing projects, going with Type L can add up to big savings.

4. Soldering

The thicker walls of Type K require more heat during the soldering process. Type L can be soldered using less heat, making it quicker to join pieces together. Less heat also means less risk of weakening the joints.

5. Pressure rating

Here‘s a big one – Type K copper can withstand 50% higher water pressure compared to Type L. The maximum working pressure for Type K copper is 1,000 PSI, versus 700 PSI for Type L. Higher pressures require Type K‘s thicker walls.

The 3 grades of copper pipe

There are three main grades of rigid copper pipe used in residential and commercial construction:

Type K

The thickest walls and strongest pressure rating make Type K suitable for supply lines and high-pressure applications. It has up to 25% thicker walls than other types.

Type L

With medium wall thickness, Type L copper is able to withstand moderate pressures while still being easy to work with. It is the most common grade for indoor water lines.

Type M

With thin walls, Type M copper is designed for low pressure applications like drains. It should never be used for pressurized supply lines.

Here‘s a table to compare the copper grades:

Pipe Type	Wall Thickness	Pressure Rating	Uses
Type K	Thickest	Highest (1000 PSI)	Water service, natural gas, DWV
Type L	Medium	Medium (700 PSI)	Indoor water lines
Type M	Thinnest	Low (100 PSI)	Drains only

This shows why Type L is recommended for most indoor water lines, while Type K is better for high-pressure needs. Type M is only for low-pressure drainage.

Burying copper pipe underground

Type K copper is approved for direct burial underground, while Type L should only be buried when placed in a protective sleeve:

Installing Type K for underground use

While Type K is rugged enough for burial, you need to take a few extra steps:

Insulate the pipe to prevent temperature expansion and contraction that could lead to joints separating or leaks.
Backfill the trench with sand, gravel or other fine materials to create a smooth and cushioned bed for the pipe. This prevents shifting and banging that could cause dents.
Avoid burial in areas with highly acidic, alkaline, or corrosive soils that could degrade the copper over time.
Use watertight joints like flared fittings or shielded couplings to prevent groundwater infiltration.
Allow for pipe expansion and contraction by using wide sweeping elbows and offset joints.

Following these best practices will help your buried Type K copper last for decades. I assist many homeowners with planning their buried water service lines and would be happy to help you pick the right materials.

Installing Type L underground

Type L copper does not have enough durability for direct underground burial. However, you can still buried it by first placing the pipe inside a protective sleeve or conduit:

Use plastic piping like PVC or flexible polyethylene to create a sleeve. Run Type L copper inside.
Use pre-insulated flexible piping that has an outer plastic shell and inner copper tube.
Place the copper inside a larger plastic or concrete conduit before burying.

This protects the Type L copper from possible punctures, shifting, or corrosive soils while still giving you the benefits of copper for your underground water or gas supply lines. The protective sleeve also makes repairs or replacements much easier down the road.

Picking between Type K and L

So when should you choose one over the other? Here are my recommendations:

Use Type K for:

High-pressure natural gas and water lines. Type K is designed to withstand gas line pressures up to 160psi.
Underground water service lines from the street to the home‘s interior. Its durability handles burial well.
Drain, waste and vent systems in commercial buildings. Type K is less prone to corrosion and puncturing.
Any piping that will be exposed to outdoor, underground, or wet conditions where durability is key.

Use Type L for:

Indoor potable water supply plumbing in most residential settings. Type L can handle the typical 45-70psi water pressure.
Hot water recirculating loops to provide instant hot water from faucets. Type L is ideal for smaller diameter pipe runs.
Low-pressure heating systems like radiant floor heat. You don‘t need Type K‘s added durability.
Tight spaces where Type L‘s flexibility makes installations easier.

Bottom line – for most homes‘ indoor plumbing, Type L will do the job just fine. Reserve Type K for the high-pressure lines or exposed/underground uses where its durability is needed.

Bending and joining the copper pipes

You can bend both Type K and L copper using tube benders designed for this purpose. Here are some tips:

Bending Type K copper

Fill the pipe with sand before bending to help prevent kinks and flattenings.
Type K requires 20-30% more bending force due to the thicker walls. Have a helper or use leverage tools.
Heat the section being bent to 350-400°F using a propane torch. This softens the pipe and makes bending easier.
Use long-radius elbow fittings at all bend points to reduce stress.
Support the pipe on both sides of the bend area to prevent sagging or deformation.

Bending Type L copper

Also fill with sand/water and heat to 350°F when bending to prevent kinks.
Keep a very gentle bend radius – Type L crimps easier than Type K due to thinner walls.
Closely monitor for flattening or deformation during bending and adjust as needed.
For tight bends, use a hydraulic bender to apply precise pressure.

For joining the pipes, I recommend lead-free solder and fluxes. Just remember that Type K requires more heat to properly melt the solder compared to Type L. I‘m always happy to demonstrate proper soldering technique – it takes some practice to master!

How long does each type last?

When installed correctly, here are the expected lifespans for each type of copper:

Type K copper:

50-70 years
Type L copper:

40-60 years

The thicker walls of Type K give it a slight longevity advantage – but both offer exceptionally long lifespans rivaling that of plastic piping.

Proper installation is key – I see lots of DIYers making mistakes that drastically reduce the pipe‘s lifespan. Working with an experienced plumber helps ensure decades of leak-free service.

Regular maintenance also keeps copper pipes flowing smoothly:

Replace old corroded fittings/unions – these often fail before pipes do.
Address drips and leaks quickly to prevent damage.
Avoid harsh cleaning products that can corrode copper.
Ensure electrical grounding remains intact for corrosion protection.

If you ever need advice maintaining your copper plumbing, don‘t hesitate to give me a call. I want to help you get the longest possible life from these durable systems.

Using copper for refrigeration

Type L copper should never be used in refrigeration systems where interior pressures will drop below atmospheric pressure. The pressure drop causes copper corrosion and fatigue cracks to form – a big safety concern.

Some specialty refrigeration systems are designed to use Type K copper safely. But this requires careful design, sizing, and material selection. And for some refrigerants, copper should not be used period due to chemical reactions that cause rapid corrosion.

My recommendation is to consult a professional HVAC engineer before attempting to use any copper piping in a refrigeration system. Have them review the complete piping design and refrigerant choice to identify potential issues. This prevents costly problems or dangerous failures down the road. I‘d be happy to connect you with some very knowledgeable HVAC pros I work with regularly.

The pros and cons of Type K and L

To sum it up, here are the primary benefits and downsides of each variety:

Type K Pros:

Withstands very high water and gas pressures
More durable for outdoor and underground uses
Handles hotter temperatures up to 800°F
Long lifespan of 50-70 years

Type K Cons:

More expensive material cost
Requires more skill to properly bend and install
Can be prone to kinking if bent too sharply

Type L Pros:

Lower material cost by 5-10%
Easier to bend by hand or with light benders
Suitable for most indoor residential plumbing
Quick and simple installations

Type L Cons:

Can‘t handle pressures over 700 PSI
Needs special care and tools when bending
Not suitable for burial or extreme heat

As you can see, both offer distinct advantages – there‘s no universally "better" option. Choosing wisely means matching the copper type to your system‘s specific demands.

Let‘s chat about your project!

I hope this detailed guide gives you confidence in specifying Type K or L copper for your next plumbing or HVAC project. If you have any other questions, don‘t hesitate to reach out. I‘m always happy to help homeowners, builders, and remodelers pick the ideal materials for the job. Let‘s talk soon!

Jill Jones
Certified Home Improvement Contractor