A Guide to Choosing the Right Plumbing System for Water Heating

When it comes to water heater installation, choosing the right type of plumbing system could be confusing. The plumbing pipes and fittings must be robust, durable, and non-corrosive so they can operate for a long time. Whether it is copper, PVC, PEX, CPVC, or galvanized steel – the installation might be tricky if you don't know the basics or do not have the right tools.

Luckily for you, we have the perfect guide for choosing the ideal plumbing system for your water heating needs and some installation tips right here.

Water heating devices need quality pipes that are durable and resistant to high water temperatures, operate at high pressures, and deliver hot water day and night without affecting the performance of the heating system.

However, choosing the right plumbing system is not easy at all. Copper plumbing was the favorite and most used so far, but new materials such as CPVC and PEX are growing in popularity.

Using the copper pipes is more complex and time-consuming as it requires soldering the fittings or compression fittings and special tools; plastic tubes are easy to connect with the watertight fittings and glue.

Note: Before using any of the mentioned pipes, check the local plumbing codes first.

Plumbing & water heaters: Basics

Properly installed plumbing is essential, as electricity and gas. The plumbing systems deliver clean water, removes wastewater, and provide hot water for the shower, laundry, and dishes. Also, we don't think about it unless something is wrong such as leaking, no hot water, smelly water

In-home water heating pipes are used to deliver cold water and move the hot water from the heater to the fixture. Also, there are different ways to do it.

Hot water delivery

Everybody likes to have a hot shower in the morning or evening. You just turn on the tap, and hot water is there. That's because your plumbing is connected to the water heater. The water heater has two pipes, one that delivers cold water, and the other one which transfers the hot water to the fixture, shower, or appliances.

Re-Circulating systems

Pipes can also be used for recirculation. This is the method that is often used for fast, hot water delivery. It uses the two-pipe system: one that gets the water from the heater to the sinks and one that takes the unused water to the heater once again.

It seems simple, but it's not. It's all about keeping the water circulating through the plumbing system utilizing the circulation pump while the pipes are insulated to keep the water heated longer, mainly when not being used or if running through space with a lower temperature.

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Auxiliary/tank systems

This system is also used to deliver hot water fast, but instead of using the recirculation system and the pump, a small heater (POU) is usually installed at the point of service. So, instead of waiting for hot water from the central water heater, the POU and short pipe length ensure instant delivery.

The pipes for these systems are somewhat simpler. It all comes down to pipes that go from the heater to the tank and from the tank to the house sinks. However, it uses a lot more energy, increasing fuel needs, and may increase monthly costs exponentially. However, it is often better for the house where water demand is lower.

Types of water pipes: Advantages & disadvantages

Now that you know how the plumbing and water heating work together, it is time to learn about different pipe types.


If there's a most used material in plumbing, it is copper. It has been used for over 40 years. The most used for pipes of any type, it is extremely reliable and resistant. However, managing and installing it can be a total headache.

Typically, it is pretty resistant to chemicals and other contaminants. Corrosion is also very rare in copper pipes, while it produces excellent results in delivering hot water.

Using it for heating water lines is always a good choice, but the price can be pretty daunting. Not only because it costs more initially but also costs more to install, as it requires sweat connections or compression fittings for joining pipes, copper is a pretty expensive choice. However, it is the most durable and reliable of all.

Copper is perfect for auxiliary plumbing systems in heaters, as they demand a more straightforward installation but excellent heating performance, which copper offers.

Standard sizes are ½" and ¾". The rigid copper pipe is recommended for a new installation while flexible for repairs, retrofits, or where solid cannot be run.

+ Extremely reliable, durable and resistant

+ Does not pollute water with contaminants or rust

+ Decent insulation keeps water hot at all times

-    Pricier than other options

-    Heavier & less flexible for re-circulating systems

Galvanized steel

Galvanized steel is one of the standard materials used for house plumbing systems and is almost as popular as copper. It works exceptionally for heaters, yet it is more prone to rusting in the long term.

For heaters, galvanized steel may work very well. However, as there is a chance of producing rust, it is not the best choice. On the flip side, galvanized steel pipes,  may last even longer than copper, up to 100 years without problems.

Galvanized steel is excellent for both auxiliary and re-circulating systems. However, it is not used as much as before due to slightly causing water-changing effects. There are some innovative galvanized choices out there that are healthier and more useful for water heating devices.

+ Offers amazing durability and resistance

+ Provides excellent insulation and heat transfer

+ Easier to install than copper

-    May cause discoloration of water

-    Almost as expensive as copper


PEX is a type of plastic that is composed of polybutylene mixed with polyethylene. This type of pipe is incredibly flexible, so it becomes straightforward to install. While it is fantastic due to how easy it is to manage and fit into homes, it is not exactly the best choice for water heaters.

It will keep the water working efficiently, but it can't be connected directly to a water heater as it could be affected by the high temperature and over time. So, you will need to use it as a retrofit or addition to an existing pipe or connect a section of other resistant material of at least 18 inches directly to the heater instead.

PEX is still resistant to heat and lasts many years before showing wear signs as long as it is not directly connected to the heat source. It works great for a re-circulating system, as it is also a little cheaper than copper and steel while delivering superior flexibility for easier installation methods.

+ Amazing versatility for re-circulating systems

+ More resistant to heat than PVC or CPVC

+ Great flexibility and strength, allowing bending without couplings

+ Excellent for cold water as well

-    May contaminate hot water due to the heavy chemical composition


PVC is simply plastic, typically white or grey, which comes in various thickness, diameters, and configurations depending on the use. It is highly versatile, durable, and reliable. PVC is also cheaper than most options out there, less expensive than steel, copper, and even PEX while still offering high-quality.

However, PVC tends to create much more contaminants inside while also slightly less resistant to hot water. Usually, PVC is better for cold-water piping, while hot water systems are not recommended as they can deform. The maximum operating temperature is 140F. The most used size is Schedule 40.

If you are going to install PVC for your plumbing water heating system, we recommend doing it on a re-circulating system. For tank systems that are too close to the heater, you may have too many problems eventually. The proper use for PVC would be alongside steel or copper to make the piping system more flexible.

+ Does not produce rust or corrosion

+ More affordable than any other option

+ Extremely easy to install due to superior flexibility

-    Does not resist as well or last as long as others

-    May grow bacteria and other contaminants

-    Not useful for connecting to heaters directly: may lose its strength

CPVC (Chlorinated Polyvinyl Chloride)

CPVC is the same PVC material but with additional chlorine that provides more durability and resistance to contaminants and corrosion. Also, CPVC helps to make clean water pipes drinkable even and works with both hot and cold water effectively.

One of the best things about CPVC is that it comes with superb insulation. Also, it is cheaper than both copper and galvanized, yet it delivers impressive flexibility none of these can offer.

For joining the pipes, it can use compression or solvent cement.

Whether it is a re-circulating or auxiliary system, CPVC may be your best choice. However, it is not as durable or resistant as steel or copper, despite being perfect for cold and hot water.

+ Extra chlorine makes pipes more durable and water drinkable

+ Easy to install: more flexible than PVC

+ Excellent for hot or cold water

-    Not recommended for places that freeze: may split if too cold

-    Not recyclable

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Types of connections used in plumbing

Soldered fittings – used to join copper pipes by soldering (also known as sweating), using flux, solder, and a torch.

Threaded fittings – can be made of steel, also plastic, and copper. For connections, use pipe dope or seal type (Teflon, for example).

Solvent weld fittings – used for connecting corresponding plastic pipes and bonded with the cement.

Compression fittings use a compression ring instead of glue or soldering and connect plastic, copper, or combination.

Note: When joining galvanized and copper pipes, use dielectric unions to prevent electrolysis.

Tip: For easy and fast pipe repairs, it is recommended to use push-on fittings as they are very easy to use.

Water heaters

Water heaters, whether electric or gas, tank or tankless, are designed to get the cold water from home plumbing, heat the water, and deliver it hot to the sink, shower, or appliances, such as washing machines dishwashers. In the tank-type heaters, it takes time to heat all the water stored inside the tank, but in tankless, water is heated while it is passing through the heat exchanger, which is on-demand.

Hot and cold water lines run parallel; they never intersect. At the spot where water enters or exits the tank-type water heater, the cold water inlet is marked with a blue ring, while the hot water side is marked with a red ring.

If the pipes are incorrectly connected (hot to cold and cold to hot), we will have an issue called plumbing crossover.

How to save

By insulating the hot water pipes, you can reduce the heat loss and keep the hot water 2-4 F hotter than pipes that are not insulated, plus conserving water. For this project, use the tube foam insulation (pipe sleeves) found in any hardware store; Lowe's, Home Depot, Home Hardware, Menards… The insulation is usually made of polyethylene, neoprene, or fiberglass.


While copper and galvanized steel are reliable and long-lasting choices, they are also more expensive and more complex to install than others. In contrast, you have PEX, a much more flexible option that resists heat even as effectively, yet it is not as cheap as PVC, which is plastic of incredible durability but with not as much resistance to heat. In this case, CPVC could be a great choice, which resists heat efficiently but is not too resistant to freezing.

In all cases, remember to keep in mind the plumbing system at your home and how it fits your water heater. This way you will be able to make a much better choice!

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