Home » Information & Service » Flues & Accessories FAQ’s

What is the difference between 304, 316 and 430 grade stainless steel?

When purchasing flues, you should always take into account the type of steel used for manufacture. In this way you invest in a durable product that will give you more for your money. Of the three types of stainless steel commonly used for the manufacturing of flues, we stock and supply 304 grade and 316 grade stainless steel flues. These two grades of stainless steel are the best quality in terms of durability and resistance to heat changes and corrosion.

304 Grade Stainless Steel (304SS) is our most popular seller and is used with most of our installations.  It’s excellent in terms of its anti-corrosion properties. This is especially important when using a closed combustion fireplace where weak acids are created during the combustion process. These acids corrode the inner walls of flue pipes. With a closed combustion fireplace installation, 304SS will last approximately twice as long as 430SS. 304SS is excellent value for money and is non-magnetic.

316 Grade Stainless Steel (316SS) is the best quality stainless steel available. It is non-magnetic and expensive. It’s often referred to as “Marine Grade Stainless Steel” as it’s typically used on seafaring vessels. This makes it especially well-suited for coastal installations where there is contact with direct spray and sea mist from the ocean. We can supply 316SS flues by special order.

430 Grade Stainless Steel (430SS) is the lowest, cheapest grade of stainless steel available and it’s the only stainless steel which has magnetic properties. Flues made from 430SS won’t last as long as 304SS or 316SS flues. The absence of Nickel in the chemical composition of 430SS leads to lower resistance to temperature changes and an increased likelihood of corrosion. It’s very low quality and rusts easily.

All stainless steel flue installations, including Marine grade 316SS require maintenance and cleaning throughout the year, especially if you are on or close to the coast.

What is the difference between a plain flue and an insulated flue?

You can spot the difference between a single skin flue and an insulated double skin flue quite easily. An insulated flue is composed of two plain flue pipes within each other, with an insulation material between them. An insulated flue has a larger diameter than a plain flue.

This insulation material results in the outside of the double skin flue becoming less hot than with a single skin flue pipe. It also prevents a lot of condensation gathering within the flue pipe. This leads to a better and more efficient passage for the smoke to exit through your flue piping.

Should I purchase a single or an insulated flue kit?

A good flue kit consists of both insulated and plain flue pipes, which is the industry standard. The flue piece which connects the plain flue pipe with the insulated flue pipe is called an insulated “end-cap”, and this item of the flue kit is installed about 300mm below ceiling level, and runs into the roof space.

The reason that we use insulated flue pipes when going via your ceiling and roof is because single skin flues get really hot. Single skin flues help to heat your house and serve as an extension of the fireplace. However, an insulated flue is the best choice for when the flue goes through your ceiling, roof space and exits via your roof itself, because an insulated double skin flue only gets warm and this is much safer. In this way your waterproofing will be more durable as the outside of an insulated flue pipe will not expand and contract upon heating and cooling down like a single skin flue pipe. Lastly, an insulated flue will vastly decrease the build-up of condensation within your flue, as the insulation prevents the hot smoke from cooling down too quickly. It is therefore preferable and safer to use insulated flue piping once the flue pipe leaves the interior of the room that is being heated.

The standard choice of material is anti-corrosive, 304 stainless steel. This will guarantee many years of safe usage of your fireplace and flue kit.

All our specials include the European CE certified Atritube flue system which is imported from Greece. All Atritube flues are made from superior 0.4 mm thick, 304 grade Stainless Steel, which is suitable to withstand the effects of long term corrosion by the harsh chemicals within the flue gases of closed combustion fireplaces. These flues are seam welded and utilise a clamp method of assembly. We therefore avoid drilling and pop riveting.

Please note that all stainless steel flues discolour overtime, due to a natural chemical reaction caused by exposure to 02 in the air and the heat from your fireplace. This natural reaction creates ‘living art’ in your home, as the colours range from golden to amber, even purples and blues, depending on how hot your fireplace is fired.

If you’d prefer something other than a ‘stainless steel look’, then you can choose to have your flues sprayed in the same colour as your fireplace i.e. black, anthracite grey, or Ivory. This is done at an additional fee and needs to be pre-ordered with your fireplace. Feel free to enquire about this when requesting a quote.

Why did we quote insulated flues when the flue pathway for installation is through the wall and up the outside of the house?

When the fireplace is in use and you are using plain flue you have a much bigger temperature variation between the air outside and air inside. This means that when the flue gasses cool off you can expect an excessive amount of condensation and soot accumulation within your flue. This will most certainly shorten the life span of your flue as it leads to corrosion as often your condensate collector won’t be able to keep up with the demand of draining the excess condensation. Insulated flues are more costly, but your flues will last a lot longer and the installation will be done according to European standards. We always recommend insulted flue with this type of installation scenario.

Can I install plain flues through my ceiling?

No, you can’t install plain flues though your ceiling, because it would be against the Fire and Safety Regulations, and your insurance will not cover you in the event of a fire. We will never install plain flues through a ceiling. We always use insulated flues for this section and for the section of flue that goes through your roof space and above the roof.

We have an existing fireplace that we want to replace. Do we need to replace the flue as well, or can we still use the old flue?

Most of the time the flue needs to be replaced as well. The reason for this is because the old flue is often a different size to the one required by your new fireplace, and the old flue may be in a bad condition. We will advise you on your options, and if there are sections of flue that are re-useable we will take that into account. It’s also important that you don’t mix 2 types of steel, as this can amplify corrosion. We standardly use 304 grade stainless steel flues which have a high resistance to corrosion and rust.

We have an existing fireplace and flue installation, but we need to replace some old flue parts. Is it better to replace the whole flue, or can we still use some of the old flue parts?

Most of the time the whole flue needs to be replaced. Often the old flue may be in a bad condition. By replacing the whole flue you’ll then have a flue installation that is new and you can avoid further installation and replacements in the near future. We will advise you on your options, and if there are sections of flue that are re-useable we will take that in to account. It’s also important that you don’t mix 2 types of steel, as this can amplify corrosion. We standardly use 304 grade stainless steel flues which have a high resistance to corrosion and rust.

What is the maximum horizontal distance that a flue pathway can be installed?

The best flue installation pathway is straight up, as this gives you the best draw. If you have no other choice, because you have to circumnavigate a beam or section of roof or wall, then the flue should travel horizontally (at a diagonal angle), and should not travel for more than 0.5 metres across. If it is more than 0.5 metres it results in bad draw and a fireplace that smokes back. It has a negative effect on the proper workings of the fireplace.

Can I have my flues sprayed in the same colour as my fireplace as an optional extra?

Yes, you can, but please order this in advance. We have a special spray booth and skilled staff who facilitate this. We charge you per item sprayed and your sprayed flues should be pre-ordered when purchasing your fireplace as we have to prepare, spray and ‘bake’ the paint on the flues. Our standard colours are black, grey and ivory-cream. However, our Charnwood Brand has an extended colour range to choose from that’s especially imported for use on Charnwood fireplaces and flue installations.

Do I need a floor plate?

A tempered glass floor plate protects your floor from the heat of your fireplace. It allows for traditional open or closed combustion fireplaces to be installed on wooden, laminate and carpeted flooring.

Tempered glass is a type of toughened, safety glass processed through controlled thermal or chemical treatments. The tempering process puts the outer surface of the glass into compression and the inner surfaces into tension. The result is tempered glass with far more strength than normal glass. Fully tempered glass can take on a higher load and is four to six times stronger than double glazed glass, so it can take the weight of your fireplace. This type of glass is used when safety, thermal resistance and strength are important considerations.  Should the glass break, it crumbles into small granular chunks rather than splintering into jagged shards. Please be aware that in the event that you drop a hard object on to the glass, you may still crack or chip the finish even though the glass is tempered.

The building regulations in South Africa stipulate that you are required to utilise a fire hearth if your flooring material near to your fireplace is of a combustible nature.  The regulations are designed for all fireplaces including closed combustion and traditional open fire places. The hearth must be of ‘adequate thickness and of an incombustible material’ (SANS 10400: v2010). It is therefore compulsory to have a floor plate if your floor is covered by a material that is not fire proof, for example wood, carpets or melamine.

The floor plate should stick out at least 5-10 cm on each side of your fireplace when it stands on top of the floor plate. Ideally you’d want about 50 cm – 70 cm of floor plate in front of your fireplace to catch any accidental spills of hot material. Keep in mind that we install between 15 and 20cm off the wall, so add the fireplace depth to this and add the overlap measurement in front.

Our floor plates come as standard rectangles with a bevelled lip. However you can custom order them from us in any shape and size. You can choose between a glass (12mm thickness) and plate steel (2mm thickness) floor plate. Keep in mind that custom orders have a minimum 2 week lead time.

The black glass has a black solid-coloured underside and features a high gloss finish. The clear glass allows for an unobstructed view of your beautiful wooden or marble flooring and won’t detract attention away from your fireplace or clash with your colour scheme. We seal the edge of this floor plate with silicone, thereby sealing out dust and dirt, so that it always remains clean on the underside. Glass floor plates allow for natural light reflection and ambience. The black steel floorplate has a black matt, solid-coloured finish and is a cost effective option if you are not using glass. Perfect for a more traditional look and style.

You could also choose to go with your own floorplate like stone, marble or granite. Please enquire about recommended sizes suitable for your fireplace.

Which size floor plate do I need?

Well, this depends on what size your fireplace is. A floor plate should have about 5-10cm on either side of the fireplace, have 15cm behind the fireplace, cover the depth of the fireplace, have and it should overlap 30-40cm in front of the fireplace. A large fireplace would use a large floor plate. We also offer custom floor plate sizes for our clients, but they have to be ‘special pre-ordered’ and may take longer. The floor plate should be installed with the fireplace.

What is the difference between your waterproofing and old fashioned ‘pap-en-lap’?

We use an EPDM Flashing combined with silicon and Megabond roof sealant (with waterproofing fibre in it) for reliable waterproofing where the flue exits your roof. EPDM’s are suitable to use with most insulated & non-insulated flues. The EPDM has a rubber boot that allow for a small amount of movement in the flue caused by wind and heat expansion. With old fashioned ‘pap-en-lap’ a waterproofing membrane (fibre material) is used in layers with lap cement or acrylic waterproofing which is painted on. The process is time consuming and messy, and any movement causes the waterproofing seal to break, which results in leaking. With EPMD’s we have found that our waterproofing is watertight. Our waterproofing is guaranteed for 18 months after the installation date.

What are pellets manufactured out of?

Wood pellet are used to fuel pellet burning fireplaces for residential heating and to fuel large boilers, they offer excellent combustion efficiency.

They are an extremely eco-friendly, natural and green fuel that’s produced without additives from 100% biological materials and wood processing waste. Most pellets are produced from offcuts from the timber industry, although some wood is sourced from sustainable forestry plantations and the clearing of alien vegetation. This waste is compressed at a very high pressure and compacted into small, 6 to 12 mm diameter cylinders which resemble ‘rabbit feed’.

Pellets burn more efficiently than other wood forms because the binding process reduces the moisture within the wood to less than 10%, which is 20% less than the average log of wood. Using pellets also reduces harmful carbon emissions when compared with other fuel sources. They are a carbon neutral product, because the combustion process used to create energy generates no increased greenhouse gas emissions. They take up very little storage space and are a cost effective option to heat your home.

TROUBLESHOOTING: What is causing the noise in my chimney / flue?

You may be hearing:

• A banging sound when the wind is gusting and howling.
• A sound like a metal bin being thrown down a gravel road.
• A rushing noise with moderate wind.
• A gentle humming noise with very strong wind.
• A whistling, flute like noise that goes away when the door is opened.
• A sound like “blowing-across-the-top-of-a-bottle” with the air inside the flue vibrating like an organ pipe.
• A noise is that is amplified in the chimney.
• A very ‘loud, roaring freight train’ (this particular noise could be a chimney fire).

Causes and possible solutions:

• Animal invaders such as birds clear out once you’ve removed their nests.
• Clicks, cracks, clangs and dongs are often caused by the thermal expansion due to heat, and these sounds are normal.
• If your chimney has no cowl, it could be the wind blowing over the top of the chimney.
• It could be a damaged, stuck or loose cowl, or a damaged chimney flue.
  It could be that you need to secure the loose flue lining in the chimney (which is banging against the chimney wall) with brackets or expanding heat resistant foam.
• The wind blowing across the chimney top maybe pulling more air up and out, causing an increased draft up the flue which creates noise. Here you could try installing a stainless steel ‘fixed type’ of chimney cowl with louvres on each of the square sides called a Turbo cowl. It diverts the wind upwards and away from the top of the chimney.
• A cowl that turns away from the wind will prevent air blowing over the chimney and therefore prevent the noise, but it’s often not a good choice in very high wind areas. However, you could install a storm cowl which is better suited to windy areas.
  Structures like trees and buildings close by may cause wind turbulence, you may have to extend your flue higher.
• When you hear a ‘flute’ like noise that goes away when the fireplace door is opened, you could open the vent sliders in small increments until the noise goes away. Installing a damper which shuts off or restricts the air flow up the chimney may also help.
• A chimney fire sounds like a loud, roaring freight train. If you suspect a chimney fire, close all the air intakes and chimney dampers to suffocate the fire. Exit the building immediately and call the fire department from outdoors.
• Unfortunately there is not much that can be done to fix noise problems if you live in a high wind area. The wind-noise within a chimney will be intermittent and will depend on the wind and weather conditions. Under safe operation and with regular maintenance of your closed combustion fireplace, it is normal to feel the wind vibrating within the flu. The suggested solutions above may help you. You are welcome to contact us for further advice.

Why is my fireplace smoking?

There are no certainties when it comes to smoking closed combustion fireplaces and a number of reasons why they could be smoking.

Dry, seasoned, hard wood weathered from the year before is the best to burn in your fireplace. Dry blue gum is great. Black wattle is ok, but burns up quicker.

Your wood is more than likely wet, as any wood sold during winter is wet. Space the wood for ventilation, use smaller pieces of wood to get the fire going (vents open all the way) and use lots of blitz. Add 2 logs when the small bits are blazing and close your vents by 2/3rds when the logs are burning well. The warmer the chimney and fireplace gets the better the air pull or draft up the chimney.

A chimney clean may be required. A build-up of creosote in the flue can cause smoking, and it can cause chimney fires. A bird’s nest can also be a problem. GC Fires offers annual chimney sweeping from November through to March. The fire rope sealing the door may need replacing. Check that the wood you stored in a the ‘decorative compartment’ of the fireplace is not smouldering.

Ensure you are not causing back drafts down your chimney by using extraction fans in the kitchen, leaving windows open etc. You want the smoke to pull up the chimney, and not into your house.

If your braai or open hearth is smoking, then you need a chimney sweep. The fireplace may not be deep enough, and you may require brickwork. You could try putting the coal cradle on bricks to raise the fire closer to the chimney opening at the top (worked at my last house).

A cowl could help with drawing the smoke up the chimney, but it’s not a guarantee. Your flue piping or chimney may not be high enough resulting in the airflow being obstructed by the roof apex or another structure on the roof. This can also happen when you live up against the mountain. Check your roof space to ensure that the chimney is intact. You don’t want sparks coming through the broken brickwork into your roof space and causing a fire.

Start with dry wood, as this seems to be the number one cause of a smoking fireplace (especially in winter when they sell you wood and swear that is dry).

How do I clean the window of my fireplace and why does it soot up?

This is rather annoying when it happens, but the solution is rather simple.

It’s usually the result of soot build up, indicating that the fuel being used in the fireplace is not burning completely. Ensure that the dampers /air controls on your fireplace remain open until the fire is well established, as this will give the fire enough air to ensure complete combustion of fuels. Adequate dry and well-seasoned kindling and fuel must be used to start and maintain the fire, and to ensure the most efficient burn possible. The chimney should be unobstructed and clean, as this allows the smoke that is produced to escape. Empty the ash pan often.

The easiest way to clean it is by using a commercially-prepared cleanser such as Limpio Cleaner. Only use a product that has been designed specifically for fireplace use or you could end up with glass discolouration. Alternatively you can clean the glass window by dipping the damp end of a cloth into the cold, white ash left over from your previous fire & gently clean the inside of the window to remove the soot build-up. However, this option takes more time and can be messy.

With either choice, you should scrub the glass using small circular strokes.
Allow the glass to dry, and then buff it with a clean cloth.

GC Fires stocks Stove & Grate polish, and fireplace glass cleaner.

How do I maintain my fireplace?

Fireplaces require occasional TLC, but only when they are completely cooled down.

Clean the outer surfaces of the fireplace with a soft, dry cloth. Don’t use abrasive cleaning materials.

Clean the glass window by using a commercially-prepared cleanser such as Limpio Cleaner or one that is recommended to you by your supplier. Only use a product that has been designed specifically for fireplace use or you could end up with glass discolouration. Alternatively you can clean the glass window by dipping the damp end of a cloth into the cold, white ash left over from your previous fire & gently clean the inside of the window to remove the soot build-up. However this option takes more time and can be messy. With either choice, you should scrub the glass using small circular strokes. Allow the glass to dry, and then buff it with a clean cloth.

GC Fires stocks Stove & Grate polish, and fireplace glass cleaner.

An annual chimney sweep can be booked with GC Fires between November & March to clean out creosote & carbon build up in your fireplace, chimney & flue. It’s best not to leave your maintenance too late, as often this creates problems.

The vermiculite firebricks in some models are replacement items & they will crack. This doesn’t affect the fireplace & they only need to be replaced when they crumble. There is no guarantee on the paint, glass and fire rope and often not on the grate or ash pan either.

All stainless steel flues turn coppery overtime ‘like living art’ & this adds to their aesthetic value. This is a natural process and can’t be avoided. If you clean your flues, do a test patch on the back of the flue out of ‘eye sight’, as some cleaning products may remove this copper colouring as well. Alternatively, you can have your flues sprayed the same colour as your fireplace. Place your order with your fireplace, before we install.

When do I need a chimney sweep?

You’ve just finished braaiing a beautiful piece of steak and take the first bite, but it tastes a bit gritty ….….could it be the spices, or sand…….or could it be soot from your chimney?

How often you clean your chimney varies on how often you use your chimney or fireplace, and what kind of wood you use. If you use your chimney often, you may need to clean it about once a year. If you use your chimney rarely, you still need to clean it at least once every two years. It is always easiest to hire a professional to clean your chimney; however, if you choose to clean it yourself, be sure to get sound directions and follow them closely.

We provide an excellent and professional service, using equipment imported from the Europe.

The real function of the chimney and flue is to carry toxic smoke and gas safely out of your home.  A clean chimney helps your household air stay breathable, especially with the high incidence of Asthma and Bronchial problems occurring today. Creosote and soot build-up is the main reason for cleaning a chimney. A chimney fire can result if the buildup of creosote and carbon on the inside surface of your flues ignites.

The extremely high temperature of a chimney fire can damage the chimney.  Heat warps metal chimneys, and cracks the tile liner on masonry chimneys.  If you don’t repair cracks and holes in the flue, the sparks generated by the fire in the fireplace could go through these openings into the attic or the framework surrounding the chimney.  This could cause a serious house fire.