The choice of universal and heat-resistant sealant for heating pipes


The sit­u­a­tion with a leak­age of the heat­ing cir­cuit is not uncom­mon, since the heat­ing sys­tem con­sists of many nodes and ele­ments, the tight­ness of which is con­nect­ed to each oth­er soon­er or lat­er is bro­ken. In addi­tion to joints, a depres­sur­iza­tion zone can also be a whole span of a pipe that is phys­i­cal­ly worn out or dam­aged due to the influ­ence of some fac­tor.

Sealant for heat­ing pipes, pro­duced in var­i­ous types and designs, helps to solve the prob­lem of a leak or ensure long-term tight­ness of the con­nec­tions of its ele­ments dur­ing the instal­la­tion of the sys­tem.

Requirements for sealing materials for heating systems

The first thing to do in case of vio­la­tion of the tight­ness of the heat­ing sys­tem is to elim­i­nate the leak­age of the coolant, thor­ough­ly or tem­porar­i­ly — before the over­haul. And the main thing that needs to be ensured when installing heat­ing is its reli­able tight­ness.

From these fac­tors fol­low the require­ments for sealants used in the instal­la­tion and repair of water heat­ing sys­tems:

  • ease of use;
  • heat resis­tance;
  • high adhe­sion and strength;
  • rather fast achieve­ment of the seal­ing effect;
  • safe­ty of use.

Read also about sealant for fur­naces.

Types of sealing compounds, their characteristics and methods of application

At the place of use, sealants for heat­ing sys­tems are divid­ed into com­po­si­tions:

  • for exter­nal use — they are applied to the place of dam­age to the pipeline from the out­side and, after cur­ing, restore the tight­ness of the sys­tem;
  • for inter­nal use (liq­uid, vol­u­met­ric action) — they are intro­duced into the cir­cuit and seal the dam­age from the inside;
  • seal­ing — applied to gas­kets and threads to improve the tight­ness of joints.

The choice of type of sealant depends on the degree of dam­age and the avail­abil­i­ty of the repair site. In addi­tion, the choice of sealant deter­mines the way the heat­ing sys­tem is pre­pared for the upcom­ing repair.

Con­sid­er sealants in rela­tion to com­mon types of dam­age and con­nec­tions of ele­ments of the heat­ing sys­tem.

Sealing compounds for external use

These sealants are pro­duced as one- or two-com­po­nent.

Con­sid­er­ing that the coolant in the pipes of the heat­ing sys­tem is not only hot, but also under pres­sure, it is nec­es­sary to seal the dam­age on the pipeline very care­ful­ly. First of all, the sealant must be designed for oper­a­tion at high tem­per­a­tures, which is indi­cat­ed on its pack­ag­ing in the form of a “heat-resis­tant” mark­ing and oper­at­ing tem­per­a­ture range val­ues.

Impor­tant! Acrylic-based sealant (acrylic) is used only for seal­ing cold water pipelines. Acrylic glue is not suit­able for repair­ing pipes of heat­ing and hot water sys­tems, since after cur­ing it is not plas­tic and there­fore col­laps­es dur­ing tem­per­a­ture defor­ma­tions of the base.

Of the one-com­po­nent com­po­si­tions for the repair of water heat­ing sys­tems, seal­ing adhe­sives based on sil­i­cone are com­mon.

Heat-resistant sealants based on silicone


To restore the tight­ness of heat­ing sys­tems from the out­side, the most com­mon use of sealants based on var­i­ous types of sil­i­cone, includ­ing rub­ber.

For the repair of steel pipes, it is nec­es­sary to use neu­tral types of sil­i­cone (a mark with this para­me­ter is on the pack­age), because the “acidic” sil­i­cone adhe­sives that are also pro­duced, which form acetic acid when cured, react with the met­al.

If the mate­r­i­al meets the nec­es­sary tem­per­a­ture require­ments, to ensure suc­cess, it is nec­es­sary to increase the effi­cien­cy and reli­a­bil­i­ty of its appli­ca­tion by addi­tion­al means. As a rule, the man­u­fac­tur­er rec­om­mends such sealants for use as a filler for cracks or holes. If anoth­er appli­ca­tion is indi­cat­ed on the mate­r­i­al, but its char­ac­ter­is­tics and poten­tial are high, the adhe­sive is quite suit­able for use. For exam­ple, a com­po­si­tion rec­om­mend­ed for seal­ing com­po­nents on an engine can eas­i­ly cope with the same task in a home heat­ing sys­tem.

And yet, giv­en the respon­si­bil­i­ty of the appli­ca­tion, it is nec­es­sary to apply sil­i­cone sealants to the pipes of the heat­ing sys­tem in com­bi­na­tion with a rein­forc­ing mesh, which is suc­cess­ful­ly used as a strip fiber­glass tape “ser­pyan­ka”.

Sealing method

A lay­er of sealant is applied to the pre­pared sur­face of the pipe (dry­ing, clean­ing, degreas­ing), on top of which coils of ser­pyan­ka are butted, then sealant again, after which the tape is already wound in turns with an over­lap of 1 cm. The num­ber of lay­ers of ser­pyan­ka with glue between them should be 4–5 , while it is nec­es­sary to pre­vent the for­ma­tion of air bub­bles or loose areas between them. The last 2–3 turns of the sick­le are made on the sec­tion of the pipe with­out glue and are tight­ened to it with a nylon clamp, which, after the sil­i­cone has cured, will be removed along with the extra turns of the tape. The top repair lay­er is made of sealant and smoothed out.

Work should be car­ried out at a tem­per­a­ture not low­er than +5 ° C, sil­i­cone should be at room tem­per­a­ture (20–25 degrees). The cur­ing of the com­po­si­tion, which occurs due to the con­tact of sil­i­cone with mois­ture, occurs depend­ing on the type of sil­i­cone and is sev­er­al mil­lime­ters per day.

MakroFlex, Mas­terteks, Titan, Mas­ter­Sil sil­i­cone sealants are prod­ucts that have proven them­selves well abroad and in EU.

Two-com­po­nent com­po­si­tions for the repair of heat­ing and hot water sys­tems are var­i­ous types of adhe­sives based on epoxy resins and polyurethane.

These com­po­si­tions are less com­mon for the pro­duc­tion of pipeline repairs, as they require cer­tain skills in main­tain­ing pro­por­tions when prepar­ing the mix­ture, they have a short “sur­viv­abil­i­ty” time of the solu­tion after mix­ing the com­po­nents and a high cost rel­a­tive to oth­er adhe­sives.


There are also one-com­po­nent polyurethane sealants, which cure on con­tact with air. The qual­i­ty of these mix­tures is also high, it takes a lit­tle longer to cure than two-com­po­nent for­mu­la­tions, and they are also sig­nif­i­cant­ly more expen­sive than sil­i­cone mate­ri­als. The main dis­ad­van­tage of polyurethane sealants is tox­i­c­i­ty dur­ing work — the room must be well ven­ti­lat­ed, and work must be done in pro­tec­tive cloth­ing and gloves to avoid get­ting glue on exposed skin.

To ensure suc­cess when using two-com­po­nent com­pounds, it is also nec­es­sary to care­ful­ly pre­pare the pipe sec­tion to be repaired and, in com­bi­na­tion with glue, use a rein­forc­ing tape — ser­pyan­ka.

Liquid sealants

Such sealants are used in sit­u­a­tions where, in order to detect a leak, it is nec­es­sary to per­form a large amount of dis­man­tling of the dec­o­ra­tive and insu­lat­ing shells of the heat­ing sys­tem (for exam­ple, the “warm floor” sys­tem), or the inten­si­ty of the leak is insignif­i­cant — there is no coolant leak, but its vol­ume decreas­es, and the pres­sure in the sys­tem with the cir­cu­la­tor run­ning is reduced.

Impor­tant! If there is no visu­al leak­age and reduced pres­sure in the heat­ing sys­tem, before adding liq­uid sealant to the cir­cuit, it is nec­es­sary to check the per­for­mance of the expan­sion tank — the pres­sure drop of the coolant may also be due to the destruc­tion of its mem­brane.

Liq­uid sealant, unlike exter­nal adhe­sives, acts on dam­age to the pipeline or radi­a­tor from the inside. The seal­ing com­po­si­tion is intro­duced into the coolant of the cir­cuit cut off from the main heat­ing sys­tem. When the sealant is added to the water, no reac­tion occurs, but in the places of leak­age, where the coolant comes into con­tact with air, the poly­mer­iza­tion of the adhe­sive begins and the seal­ing of the dam­age begins.

Many vari­eties of liq­uid sealants are pro­duced, focused on use in cer­tain heat­ing sys­tems, dif­fer­ing in the type of coolant, the fuel of the heat­ing unit, the mate­r­i­al of the pipeline, radi­a­tors, etc.

If the leak­age of the sys­tem is not sig­nif­i­cant, and the seal­ing com­pound is select­ed and used cor­rect­ly, then the prob­a­bil­i­ty of suc­cess in repair­ing dam­age from the inside is high.

Impor­tant! In heat­ing sys­tems with pipes and radi­a­tors made of steel or alu­minum, if seal­ing is nec­es­sary, it is per­mis­si­ble to use a vehi­cle cool­ing sys­tem repair agent, but not a pow­der type deposit­ed in the low­er part of the pipeline and its ele­ments, but liq­uid.


Mode of application

This means of deal­ing with leaks in heat­ing sys­tems is rel­a­tive­ly new, and there is no uni­ver­sal tech­nol­o­gy for its use, although the prin­ci­ple of oper­a­tion for all liq­uid for­mu­la­tions is com­mon.

The sealant is pur­chased in accor­dance with the char­ac­ter­is­tics of the heat­ing sys­tem installed in the hous­ing. In addi­tion, when buy­ing a com­po­si­tion, you need to know how much coolant the heat­ing cir­cuit holds in order to pur­chase the sealant in the required quan­ti­ty — the adhe­sive instruc­tions indi­cate the con­cen­tra­tion in which it must be present in the sys­tem.

The use of each type of such a sealant has its own nuances: the admis­si­bil­i­ty of the pres­ence of fil­ters in the cir­cuit, the method of intro­duc­ing the com­po­si­tion into the coolant, the dura­tion of action, the size of the dam­age, the pos­si­bil­i­ty of the pres­ence of glue in the sys­tem after the effect has been achieved, etc. The algo­rithm for seal­ing with a liq­uid com­po­si­tion is described in detail in the instruc­tions for its use, but often for inde­pen­dent per­for­mance of this oper­a­tion it is nec­es­sary to have a spe­cial tool or equip­ment, such as a com­pact elec­tric pump for the ini­tial intro­duc­tion of the sealant into the cir­cuit and its com­plete dis­so­lu­tion and uni­form dis­tri­b­u­tion through­out the vol­ume of the coolant. There­fore, with­out hav­ing prac­ti­cal skills in this mat­ter, it is bet­ter to turn to spe­cial­ists who will per­form this pro­ce­dure with­out pos­si­ble neg­a­tive con­se­quences such as clog­ging the sys­tem or fail­ure of its nodes.

Sealing compounds

Many years ago, linen tow was used to seal thread­ed joints, the strands of which were wound on the exter­nal thread and cov­ered with red lead on nat­ur­al dry­ing oil (GOST), after which the joint was assem­bled along the thread. With the advent of mod­ern arti­fi­cial heat car­ri­ers in heat­ing sys­tems, tow par­tial­ly lost its effec­tive­ness due to the high degree of per­me­abil­i­ty of antifreezes and gave way to FUM tape, although it is used in com­bi­na­tion with a spe­cial Uni­pack paste, which also con­tains flax fibers, when assem­bling cast iron pipelines of large diam­e­ters or sim­ply for lack of flu­o­ro­plast.

FUM-tape is a syn­thet­ic flu­o­ro­plas­tic mate­r­i­al of a mat­te, less often trans­par­ent col­or, which, due to the flu­o­rine con­tent, endures mechan­i­cal and ther­mal influ­ences with­out com­pro­mis­ing its qual­i­ties.

Depend­ing on the con­di­tions of use, flu­o­ro­plas­tic tape is pro­duced in sev­er­al vari­eties:

  • indus­tri­al, con­tain­ing 20% ​​vase­line;
  • house­hold;
  • for acid envi­ron­ments;
  • for sys­tems with spe­cial require­ments for the clean­li­ness of the envi­ron­ment.

Impor­tant! Fum-tape is used for seal­ing joints in sys­tems with cold and hot water at a max­i­mum pres­sure val­ue of 9.5 MPa.

Appli­ca­tion rules:

  • the tape is wound tight­ly, with light ten­sion, in the direc­tion of the thread;
  • the end of the tape should not be locat­ed at the end of the joint.

FUM tape is wound on the thread with a num­ber of lay­ers depend­ing on the thread diam­e­ter:

  • Ø 16–25 mm — 3 lay­ers;
  • Ø 25–42 mm — 4 lay­ers.

The num­ber of lay­ers is very con­di­tion­al, since low-qual­i­ty mate­r­i­al will require twice as much con­sump­tion.


Dis­ad­van­tages of FUM tape:

  • when assem­bling coarse thread­ed con­nec­tions, the tape is torn and squeezed out;
  • does not have adhe­sion to the sur­face of mate­ri­als;
  • does not pro­vide seal­ing for threads with a diam­e­ter of more than 25 mm, there­fore it can­not be used when assem­bling heat­ing radi­a­tors.

For seal­ing thread­ed con­nec­tions, liq­uid and pasty com­po­si­tions are also used, which can be dry­ing or remain elas­tic through­out the entire ser­vice life.

An exam­ple is the same non-hard­en­ing Uni­pack paste with flax fibers in the com­po­si­tion, which is used as an inde­pen­dent mate­r­i­al that pro­vides not only the tight­ness of thread­ed con­nec­tions, but also their pro­tec­tion against cor­ro­sion, as well as ease of dis­as­sem­bly

Dry­ing pastes are sol­vent-based sealants, a mod­ern mate­r­i­al that is plas­tic when assem­bling the joint and hard­ens after a cer­tain time. For more effi­cient use, they can be used in com­bi­na­tion with a linen strand, which slows down the assem­bly process; after dry­ing, they pro­vide a strong con­nec­tion with­out shrink­age dur­ing oper­a­tion.

The dis­ad­van­tage is the impos­si­bil­i­ty of tight­en­ing the thread­ed con­nec­tion with­out com­pro­mis­ing the tight­ness of the joint.

Anaer­o­bic sealants are ready-to-use mix­tures that dif­fer in prop­er­ties depend­ing on the appli­ca­tion con­di­tions (pres­sure, tem­per­a­ture, vibra­tion), thread diam­e­ter, assem­bly den­si­ty, etc.


  • ease of use;
  • low labor inten­si­ty of the process due to lubri­cat­ing qual­i­ties;
  • seals the thread­ed con­nec­tion even with low assem­bly force;
  • a wide range of work­ing pres­sures of the medi­um in the pipeline;
  • easy removal of excess mix­ture at the end of work;
  • the pres­ence of species with vary­ing degrees of fix­a­tion;
  • the opti­mal ratio of the “price-qual­i­ty” indi­ca­tor.

Anaer­o­bic sealants are applied to both con­nect­ed thread­ed sur­faces (inter­nal and exter­nal), pre­vi­ous­ly cleaned and degreased. The instruc­tions for use, as a rule, indi­cate the air tem­per­a­ture accept­able for the pro­duc­tion of work — usu­al­ly it is about 15 degrees Cel­sius (if the com­po­si­tion cur­ing accel­er­a­tors are not used in the process).

An exam­ple of anaer­o­bic adhe­sive is the uni­ver­sal heat-resis­tant sealant for heat­ing pipes PERMATEX 59214, which has proven itself well in the Euro­pean mar­ket.

The seal­ing and seal­ing com­pound of medi­um strength, heat and vibra­tion resis­tant, allows adjust­ment of the thread­ed con­nec­tion with­in 24 hours after assem­bly. The max­i­mum work­ing pres­sure is 700 atm., the lim­it­ing tem­per­a­ture is + 200°C.


Sealant for the repair and con­nec­tion of heat­ing pipes is a mate­r­i­al that can­not be dis­pensed with when installing a heat­ing sys­tem, so it is dif­fi­cult to over­es­ti­mate the impor­tance of choos­ing this mate­r­i­al when installing and repair­ing coolant cir­cuits. From which it fol­lows that when buy­ing adhe­sives, pref­er­ence should be giv­en to prod­ucts from well-known man­u­fac­tur­ers, whose rat­ing on the Euro­pean mar­ket is quite high.


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