All about the pressure in the heating system of a multi-storey building


Heat­ing in a mul­ti-storey build­ing is a com­plex engi­neer­ing sys­tem, the cor­rect oper­a­tion of which is fea­si­ble only if many para­me­ters com­ply with the stan­dards. These para­me­ters include the pres­sure in the heat­ing sys­tem of a mul­ti-storey build­ing, due to which safe­ty, effi­cien­cy, and dura­bil­i­ty are achieved.

The essence of the phenomenon

So, it is the pres­sure in the heat­ing sys­tem of an apart­ment build­ing that deter­mines how effec­tive it will be. The pres­sure cre­at­ed ensures that the coolant reach­es the most dis­tant radi­a­tors and pipes, the tem­per­a­ture evens out in all rooms.

The opti­mal val­ue of this para­me­ter also reduces heat loss­es, the water is in the radi­a­tors with the same tem­per­a­ture that was reached in the boil­er.


Water pres­sure in a pri­vate house or oth­er build­ing is divid­ed into sev­er­al groups:

  • Sta­t­ic. The para­me­ter deter­mines how intense­ly the water “press­es” on radi­a­tors and pipes at dif­fer­ent heights.
  • Dynam­ic. It is formed in the process of cir­cu­la­tion of the coolant along the cir­cuit, it is it that con­tributes to the wear of the ele­ments.
  • Max. A crit­i­cal val­ue, the achieve­ment of which is like­ly to pro­voke an acci­dent.

In most Euro­pean hous­es, this indi­ca­tor is at the lev­el of 7 atmos­pheres, this is quite enough for cor­rect func­tion­ing. How­ev­er, cer­tain phe­nom­e­na change the val­ue (crit­i­cal­ly low lev­el — 5 atmos­pheres), which caus­es unde­sir­able effects.

What does it depend on?

The pres­sure in the water heat­ing sys­tem of a pri­vate house varies depend­ing on sev­er­al fac­tors:

  • The degree of wear of heat­ing devices. The obso­les­cence of tech­nol­o­gy invari­ably leads to a drop in the lev­el of effi­cien­cy. There is only one way out — the pur­chase of new devices (main­ly for pumps).
  • The degree of over­grow­ing of devices with hard­ness salts and sludge. Exit — qual­i­ty con­trol of the coolant, peri­od­ic flush­ing of the heat­ing sys­tem.
  • The pow­er of the units sup­ply­ing the coolant. For mul­ti-storey build­ings, these units are heat points, for cot­tages — cir­cu­la­tion pumps. The far­ther the build­ing is locat­ed from the heat point, the worse things are.
  • Loca­tion of the apart­ment. Of course, under ide­al con­di­tions, the pres­sure in each pipe and each radi­a­tor is the same, but this is not always pos­si­ble to achieve. The min­i­mum pres­sure is fixed in the cor­ner rooms — the fur­thest from the main ris­ers.
  • Pipe diam­e­ters. If, dur­ing the repair process, the res­i­dents replaced the pipes in the apart­ment with prod­ucts with a larg­er diam­e­ter than that of the inlet pipeline, the val­ue does not change, but the speed of water move­ment decreas­es slight­ly. Inter­est­ing­ly, plas­tic pipes dur­ing oper­a­tion can grad­u­al­ly become wider than the orig­i­nal diam­e­ter, which prac­ti­cal­ly does not affect the pres­sure in the sys­tem. How­ev­er, it hap­pens that the inner lay­er of the met­al-plas­tic pipe exfo­li­ates due to tem­per­a­ture and clogs the pas­sage. Then the cir­cu­la­tion pres­sure drops sharply, some­times to zero (this hap­pens extreme­ly rarely if the build­ing is locat­ed near the boil­er room: the coolant tem­per­a­ture exceeds the stan­dard for met­al-plas­tic).

See also: caus­es of pres­sure drops in boil­ers.

Common Causes of Pressure Drop

If there are prob­lems with the heat­ing of the house, it is like­ly that the prob­lem is relat­ed to pres­sure. In most cas­es, the sys­tem is aired, the cir­cu­la­tion pres­sure drops, some­times to zero. It is solved by bypass­ing the coolant in the oppo­site direc­tion to the “dis­charge”, that is, they close the sup­ply line, after the tap, open the drain valve or plug. Back pres­sure eas­i­ly releas­es air into the atmos­phere. The sec­ond most com­mon rea­son: sup­ply valves on ris­ers are clogged with sludge (accord­ing to the project, valves are installed on ris­ers to reg­u­late pres­sure, not ball valves), as well as depres­sur­iza­tion of the heat­ing sys­tem. The most vul­ner­a­ble places in this regard are con­nec­tions and joints. Of course, some­times the pipes them­selves break if they have already exhaust­ed their ser­vice life, become dilap­i­dat­ed, rusty, and thinned. A leak leads to a drop in sta­t­ic pres­sure, but if this para­me­ter is nor­mal, the prob­lem lies else­where. To sim­pli­fy the search process, the main sec­tions are checked one by one, when a defec­tive sec­tion is found, it is cut off, restored, and com­pact­ed.
If you can­not find a leak on your own, you need to involve spe­cial­ists. They take a dif­fer­ent approach: the sus­pi­cious area is drained and filled with air, the exit of which is able to detect even a micro­c­rack.

Even if this method shows the health of the pipeline, the prob­lem prob­a­bly lies in the boil­er:

  • The heat exchange cir­cuit is cov­ered with scale. This prob­lem is espe­cial­ly rel­e­vant for sys­tems where the coolant is not of high qual­i­ty (hard water). The scale itself on the heat exchang­er does not affect the cir­cu­la­tion pres­sure (it affects the effi­cien­cy of the boil­er), but the scale par­ti­cles exfo­li­at­ed from the walls of the heat exchang­er are dan­ger­ous: they clog fil­ters, auto­mat­ic valves, valve seats, caus­ing a pres­sure drop, some­times a com­plete mis­align­ment of the heat­ing sys­tem;
  • Dam­age to the expan­sion tank (leads to air­ing or to a sharp increase, as a result — a rush and, accord­ing­ly, a leak);
  • Destruc­tion of the heat exchang­er due to water ham­mer (main­ly due to the instal­la­tion of ball valves instead of the rec­om­mend­ed valves for feed­ing the heat­ing sys­tem);
  • Micro­c­racks on the tank of the exchange cir­cuit, the appear­ance of which is pro­voked by the ini­tial­ly low qual­i­ty of pro­duc­tion or a long peri­od of oper­a­tion.

It is nec­es­sary to elim­i­nate leaks, block­ages, and only after that raise the pres­sure to oper­at­ing pres­sure. Main­te­nance work on the heat­ing sys­tem is car­ried out only after the pres­sure has been reduced to sta­t­ic pres­sure or, if nec­es­sary, com­plete­ly emp­tied. Such works include:

  • Fil­ter clean­ing;
  • Replace­ment of faulty devices;
  • Drainage of the water sys­tem in con­nec­tion with the ces­sa­tion of gas sup­ply in win­ter (emer­gency work on the gas main) to pre­vent freez­ing;
  • Flush­ing the heat­ing sys­tem from deposits and scale.


In order to check the com­pli­ance of the val­ue with the stan­dards, some con­scious util­i­ties car­ry out hydraulic tests of the heat­ing sys­tem:

  • Cold test­ing. All main ele­ments are filled with cold water (tem­per­a­ture not low­er than +5 degrees Cel­sius), the achieved para­me­ter is fixed. Clause 4.6 (INTERNAL SANITARY-TECHNICAL SYS­TEMS-SNiP 3–05-01–85): Test­ing of water heat­ing and heat sup­ply sys­tems should be car­ried out with the boil­ers and expan­sion ves­sels turned off by the hydro­sta­t­ic method with a pres­sure equal to 1.5 work­ing pres­sure, but not less than 0.2 MPa (2 kgf / sq. cm) at the low­est point of the sys­tem. The sys­tem is rec­og­nized as hav­ing passed the test if, with­in 5 min­utes of being under test pres­sure, the pres­sure drop does not exceed 0.02 MPa (0.2 kgf / sq. cm) and there are no leaks in welds, pipes, thread­ed joints, fit­tings, heat­ing appli­ances and equip­ment. If it was pos­si­ble to meet these stan­dards, launch is allowed. If the air tem­per­a­ture is below +5, then the test is car­ried out with com­pressed air.
  • Hot test­ing. As a rule, it is held before the offi­cial start of the heat­ing sea­son. A hot coolant is pumped under pres­sure close to crit­i­cal for a par­tic­u­lar sys­tem. The absence of prob­lems sug­gests that dur­ing the heat­ing sea­son there will be no excess­es.

Prevention measures

In order not to have to urgent­ly raise or low­er the pres­sure, mechan­i­cal fil­ters should be reg­u­lar­ly inspect­ed for block­ages. Also, do not for­get about the expan­sion tank, if nec­es­sary, pump air up to the val­ue indi­cat­ed in the pass­port of the boil­er or expan­sion tank. With­out fail, the heat­ing sys­tem must be equipped with a safe­ty group (auto­mat­ic air vent + auto­mat­ic pres­sure reliev­er), with the help of which air is eas­i­ly bled, excess coolant is drained. An exam­ple of a fac­to­ry-ready secu­ri­ty group is in the first pho­to of this arti­cle.


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