Installing a sandwich pipe in a bathhouse with your own hands

In modern steam rooms, stone stove chimneys are being massively replaced by steel structures. A properly selected sandwich pipe for a sauna allows you to get rid of a lot of problems that accompany brickwork, and at the same time reduce the cost of building a stove. After all, many of the work on installing a sandwich chimney in a bathhouse are quite easy to do with your own hands.

General requirements for a chimney in a bathhouse

The dimensions and design of the chimney in a sandwich pipe bath are influenced by the following requirements:

The optimal length of the pipe from the stove to the fungus on the roof is 5 m.
The pipe is mounted vertically, without ledges. The permissible deviation of the pipe from the vertical is 30 degrees, with a maximum deviation to the side of 1 meter.
If the size from the roof to the pipe head is more than 1.5 m, install a brace to secure the structure.
If the roof is covered with flammable materials, install a spark arrestor mesh with 5x5 mm cells at the end of the pipe.
The pipe on a pitched roof should protrude 50 cm above the ridge. The pipe on a flat roof should be located 1 m above the roof.
The horizontal part of the smoke exhaust tract is up to 1 m.
The joints of pipe elements must remain visible; they are not allowed to be located inside the roof slabs.
It is prohibited to place cleanouts and horizontal outlets in the attic. The pipe in the attic should point upward.

We check the quality of purchased sandwich pipes

Their reliability can be determined even upon inspection:

Welded ones must be designed carefully and not differ in color from the metal itself.
The pipe must be of the correct rounded shape.
Check the alignment of the inside of the pipe with the outside. There should be no deviations of more than 1 mm, otherwise joining the sections will be difficult.
All figured components - tee, head, cap - should not have obvious joints, rough seams or other defects.
All parts of the stove chimney must be marked. The brand, steel thickness, barcode, diameter, name are indicated.
Packaging: corrugated cardboard with branded tape. Each piece is wrapped separately.
Laser and plasma welding is characterized by increased reliability. It does not damage the galvanized coating and prevents corrosion at the joints.
2-3 mm of undercooking is allowed at the end of the modules.

How to choose a sandwich chimney for a bathhouse

A sandwich chimney is made by connecting individual parts of a 1 m long chimney. Each section of the structure consists of three components - an inner and outer pipe with a heat-resistant layer. The chimney also requires fastening elements and auxiliary products. Double-wall chimneys are produced in many designs and differ in their parameters - diameters, type of insulator and its thickness, pipe material, etc. To avoid mistakes when choosing sandwich pipe elements, use the recommendations.

Determining the cross-section of a chimney for a bathhouse

The chimney must have the same cross-section as the outlet flange of the stove. If necessary, you can determine the cross-section of the pipe for the furnace by calculation using the requirements of SNIP:

For a 3.5 kW boiler, pipes with a cross section of 0.14 × 0.14 m are used.
For a boiler with a power of 3.5–5.2 kW - 0.14 × 0.2 m.
For a boiler with a power of 5.2-7 kW - 0.14 × 0.27 m.

Find out or calculate the thermal power of your stove and determine the cross-sectional area of the chimney that will ensure compliance with the requirements of SNIP. Select a sandwich chimney that has a round shape according to its estimated cross-sectional area.

Selection of bath pipes by material

The internal chimney pipe is made of stainless steel.
If possible, choose a pipe with the thickest wall, it is more rigid. Do not buy a pipe with a wall less than 1 mm. The outer pipe can be made of any metal, even galvanized steel. It is better that the outer pipe is also made of stainless steel - when heated, the material practically does not elongate, which cannot be said about a galvanized sheet. Stainless steel pipes are only identical in appearance. When purchasing, you can determine the quality of products as follows:

Try to find out the metal composition of the pipe. High-quality samples are made from austenitic steel with the addition of molybdenum, chromium, and nickel. These substances help resist corrosion and acidic substances.
Inspect the pipe welds. Burnt seams are not allowed.
Stainless steel pipes are expensive. You can reduce the cost of installing a sandwich pipe in a bathhouse if you make a combined chimney: in a steam room with high humidity, high fire safety requirements and in order to give a representative appearance, install stainless steel elements, in other places - galvanized ones.
For a bathhouse, buy sandwich pipes with heat-insulating material that can withstand temperatures of more than 800 degrees. Asbestos, mineral-bonded, and expanded clay insulation have these characteristics.
The thickness of the insulator layer with the same material properties can be from 20 to 60 mm, so before purchasing, be sure to inquire about the composition and properties of the insulation.

Connection of pipe elements for a bath

On the market you can find samples that are joined and fixed with each other in various ways - flange, bayonet, “cold bridge”, but for a bath it is recommended to choose between a “smoke” or “condensate” connection.
The difference between the connections is as follows:

The “smoke” connection guarantees that there is no leakage of smoke through the joint into the room. But, on the other hand, condensation flowing down the walls of the pipe can get inside the sandwich through the cracks and damage the insulation.
In a “condensate” connection, the inner pipe of the upper sandwich fits into the socket of the lower pipe, so moisture does not get on the insulation. In this case, there is no guarantee that smoke will not leak outside.
The customer independently chooses the connection method. For indoor installations, the “smoke” method is usually chosen, because a small amount of condensate forms in sandwich chimneys.
When purchasing, check the quality of the modules joining. A good connection will be ensured by samples from one manufacturer.

Brick and metal chimney maintenance

There are many different ways to clean a chimney. Perhaps the most popular of them is cleaning the pipe in winter using snow, which must be thrown from above. However, the effectiveness of this method is low. It is better to use one of the methods that bring much more noticeable results.

Chimney cleaning - photo

Way	Description
Cleaning with a brush	Cleaning with a brush is an old and proven method that has been used since time immemorial. It allows you to achieve an excellent effect, but for this you will have to work hard. In addition, be prepared for the fact that a lot of soot will get on you - this work is very dirty.
Chimney cleaning with weights on a cable	Cleaning the chimney with a cable weight is another mechanical cleaning method. Like cleaning a pipe with a pipe cleaner, it’s effective, but it means you’ll have to tinker with it and get pretty dirty with soot along the way.
Using a fan	You can also install a fan at the top of the pipe that will work for suction. It will pull soot out of the chimney, but you need to prepare for the fact that the space around the bathhouse will then be contaminated with it.
Aspen firewood	There is an easier way - you need to throw aspen firewood into the stove. As a result, a powerful draft will arise, and the soot will be knocked upward. In the dry and intense heat that aspen creates, the resinous substances that settle in the pipe quickly burn out if you heat the bathhouse with coniferous wood.
Chimney cleaner	Cleaning with chemicals. There are different options here, for example, you can throw special preparations into the sauna stove along with firewood that enhance cravings. A significant advantage of this method over cleaning with aspen firewood is that the compositions used contain special substances that additionally loosen the soot. As a result, it easily moves away from the inner surface of the chimney.
Washing and heating the furnace	Another option is to pour several liters of water into the pipe, then heat the stove for a long time.

To extend the service life of the chimney, it is necessary to periodically inspect all joints and check the general condition of the structure in order to notice problems that may appear in the early stages. As noted above, if you install a metal chimney in your bathhouse, its lower pipe will need to be changed periodically, since it heats up much more and therefore becomes unusable faster.

If you strictly follow the technology, a home-made brick or metal chimney will remove smoke well and retain heat well. In this case, the risk of fire is reduced to almost zero. Both metal and brick structures are very durable, so it will not be long before you feel the need to build or install a new chimney in your bathhouse.

Preparatory work before installing the pipe in the bathhouse

Before installing a sandwich pipe in the bathhouse, or more precisely at the stage of construction of the stove foundation and roof, check the location of the chimney axis.
The pipe should not cross the rafters and floor beams of the attic and roof and should be located at a distance of less than 25 cm from the wall. It is possible to carry out preliminary installation of the stove and chimney in a minimal amount. The work is completed when at least the subfloor is ready and the wooden elements of the roof are secured. Place the oven on the subfloor. Place the device in its normal position in a vertical plane, taking into account the height of the floor “pie” and the thickness of the floor covering. Lower the plumb line from above to the center of the furnace outlet flange and see the results. If the load-bearing elements of the roof do not intersect with the plumb line, cut off the excess elements to allow installation of the pipe. Postpone major work until construction work on the floor is completed.

Instructions for installing a chimney in a bathhouse

The procedure for installing a sandwich pipe for a stove in a bathhouse looks like this:

Install a ceiling pass-through assembly (CPU) where the pipe passes through the ceiling.
Install the first pipe element, which should be single-walled, onto the exhaust flange of the furnace. The sandwich pipe is installed starting from the second level.
Install the double-wall pipes and the remaining elements of the chimney one by one (tees, elbows - if required by the pipe design), lead them through the ceiling, secure them together and to the walls.
Insulate the pipe penetration into the attic.
An inspection with a stand should be installed up to the attic for inspecting the internal cavity of the pipe and cleaning it from soot and other similar elements.
Continue installing the chimney in the attic and lead the pipe to the roof. Only sandwich pipes are allowed to be installed in the attic; additional elements are prohibited.
Apply thermal insulation where the pipe passes through the roof.
Secure the outer part of the pipe with guy wires (if it protrudes high above the roof). Install a spark arrestor and fungus on top of the finished product.

Fastening a sandwich pipe in a bathhouse to the wall

The pipe is narrowed on one side, so for assembly it is enough to install one pipe into the other.
To seal gaps and joints, a chimney sealant that can withstand temperatures of 1000 degrees is used. The absence of gaps in the connections increases traction. When connecting pipes, adhere to the following rules:

For internal pipes, sealant is applied to the outside of the upper internal pipe.
On the outer pipes - on the outer surface of the upper pipe.
At the joints of a single-wall pipe with a sandwich chimney or with other modules - from the outside, around the circumference.
Sandwich pipes are connected to each other with clamps on one side.
Sandwich pipes are connected to tees and adapters with clamps on both sides.
The pipes are attached to the wall using brackets every 2 m.
The tees are fixed to the supporting structures with brackets.

Design Features

Modern channels for removing smoke from sauna stoves are assembled from pipe sandwich parts. The products are popular among owners of country houses, despite the large selection of materials for creating chimneys.

The sandwich pipe is a double-circuit design. It consists of the following main parts:

The double-circuit pipe has become widely used by homeowners when installing chimneys. It came to replace single-circuit similar products made of 0.5 mm thick steel. After all, a steel pipe product is not suitable for installing a smoke exhaust duct outside a building. The reason for this is its design, which does not retain heat in the off-season and winter period of the year. In cold weather, condensation forms in a steel channel with one circuit due to a sharp temperature difference. Therefore, the traction effect in the chimney decreases, and even traffic jams appear.

The internal contour of the pipe sandwich product for removing combustion products is made of stainless steel. Its one-piece design is manufactured using TIG welding. It allows you to make neat, thin seams.

The outer casing is also made by welding from stainless or galvanized steel. The second type of metal allows manufacturers to produce more affordable products. In cooperation with a construction and installation organization, you can also order a chimney made of a sandwich pipe with an outer casing coated with enamel in the required color.

The thermal insulation layer in a product with two circuits is created from a material that is resistant to fire. Manufacturers use high-density mineral wool made from basalt raw materials. Typically the thickness of the thermal layer is 25-100 mm. Design engineers select this parameter taking into account the specifics of installation work and the conditions of use of the chimney.

The ends of the sandwich parts for the smoke exhaust duct are made in the form of sockets and narrowed ends. This interface system simplifies the installation process and allows elements to be tightly joined. To increase the strength of joints when installing a chimney, special clamps are additionally used. Depending on the design features of the smoke exhaust channel and the work conditions, parts connected to each other and other elements of the furnace system using flanges can be used.

The passage of a chimney in a bathhouse through the attic floor

Installation of a sandwich pipe in a bathhouse must be carried out in accordance with the requirements of SNIP regarding thermal insulation of the chimney when passing through wooden floors.
The temperature in the firebox, especially if fired with wood, reaches 800–1000 degrees. It easily heats the chimney (and the boards in the ceiling) to a high temperature that is critical for wood. To ensure safe passage of pipes through the attic floor, a ceiling-pass assembly (CPU) is used. The product is made in the form of a box measuring 300 x 300 mm. There is a hole in the horizontal wall through which the sandwich pipe passes. Polyurethane foam made of stainless steel or galvanized iron can be found in finished form on the market. The device is mounted in the ceiling opening before the pipe is assembled.

Thermal insulation of the pipe in this place is performed in the following order:

Install the polyurethane foam into the opening in the ceiling along with the heat insulator and secure it.
Install the sandwich pipe on the lower elements so that the connection is higher than the attic floor.
Make sure that there is a gap of at least 130 mm between the pipe and the ceiling.
This gap can be left unfilled, but it is better to fill the internal space between the pipe and the walls of the polyurethane foam with mineral wool.
Cover the joints at the bottom and top with stainless steel sheets. Also place a heat insulator between the sheets and the ceiling.

Types of ceiling penetrations

The chimney through the ceiling and roof of the bathhouse passes through protected openings. One of the main conditions for the safety of people in a heated building is heating the roof, ceiling and walls structures near the pipe to a temperature not exceeding 50 °C. Fire safety requirements for the installation of chimneys are set out in SP 7.13130.2013. Heating, ventilation and air conditioning. Fire safety requirements.

To pass the pipe from the bathhouse through the ceiling or roof structure, a through-ceiling assembly is installed - a prefabricated box with flanges. Insulation is placed between the flanges. The box insulates the surrounding structures from the heated surface of the pipe. You can make it yourself, it's not very difficult.

For the speed and convenience of passing pipes through the roof and ceiling, the industry produces ready-made passage units. They are round and square. As a rule, these units are made of stainless steel with a heat insulator, sometimes mineralite - cement boards with fiber fiber (mineral, cellulose). Previously, asbestos-cement slabs (flat slate) were used, but asbestos is carcinogenic, and their use indoors is prohibited by sanitary standards. This is still not a roof or a fence, the asbestos dust from which is washed off by rain and carried away by the wind. Sometimes there are pass-through units made of galvanized steel, but in humid bath air they will quickly rust, so they are used only as a last resort.

Mineral wool is mainly used as insulation (thermal insulator), but expanded clay, clay, and a mixture of clay and expanded clay are allowed. Mineral wool has a very significant drawback - when wet, it becomes thermally conductive (due to water), and after drying it does not completely restore its thermal insulation properties.

If the flange or body of the passage unit is made of steel, and the ceiling structures include flammable elements (wood, foam), then a layer of mineral wool must be laid between the structures and the steel elements. Otherwise, the structures may char or even burn.

The passage of a chimney in a bathhouse through the roof

Let's consider the features of the passage of a sandwich pipe through the roof:

Make sure that the distance from the pipe to the ceiling wall is at least 130 mm.
Cut out the roof sheet from a steel sheet. It is a sheet with an internal hole equal to the diameter of the pipe, and dimensions larger than the opening in the ceiling.
Place the roofing sheet on the pipe.
Pass one end of the pipe into the roof opening from the attic side, install the other end into the lower pipe.
From the roof side, install a lead base (corner roof groove) on the pipe and lower it onto the roof. Tap the base with a hammer and press it to the surface of the crusher.
From the attic side, fill the gaps between the pipe and the ceiling with basalt cardboard and basalt wool.
Lift the roof sheet all the way up and secure it with wood screws.
To ensure a sealed joint, cover the joint with rubber-based asphalt roofing sealant.

Video instructions for installing a sandwich pipe in a bathhouse with your own hands: Installing a sandwich chimney is a labor-intensive job that requires concentration and attention from the performer. The main thing is to choose high-quality materials that will ensure the reliability and safety of heating the bath.