Taboo 1: the main materials, equipment and products used in the construction are lack of technical quality identification documents or product certificates that meet the current standards issued by the state or the Ministry. Consequence: the project quality is unqualified, there are potential accidents, and it cannot be delivered and used on time, so it must be reworked and repaired; the construction period is delayed, and the input of labor and materials is increased. Measures: the main materials, equipment and products used in the water supply and drainage and heating and sanitation engineering shall be provided with technical quality appraisal documents or product certificates that meet the current standards issued by the state or the Ministry; the product name, model, specification, national quality standard code, delivery date, manufacturer's name and location, delivery product inspection certificate or code shall be indicated.


Taboo 2: the necessary quality inspection is not carried out before the installation of the valve. Consequence: during the operation of the system, the valve switch is not flexible, the closing is not strict and the phenomenon of water (steam) leakage occurs, causing rework and repair, even affecting the normal water supply (steam). Measures: pressure strength and tightness test shall be conducted before valve installation. 10% of each batch (of the same brand, specification and model) shall be selected for the test, and no less than one. For the closed-circuit valves installed on the main pipe to cut off, strength and tightness tests shall be conducted one by one. The valve strength and tightness test pressure shall comply with the provisions of code for acceptance of construction quality of building water supply and drainage and heating engineering (GB 50242-2002).


Taboo 3: the specification and model of the installed valve do not meet the design requirements. For example, the nominal pressure of the valve is less than the system test pressure; when the pipe diameter of the water supply branch pipe is less than or equal to 50 mm, the gate valve is used; the stop valve is used for the dry and vertical pipes of hot water heating; the butterfly valve is used for the water suction pipe of the fire pump. Consequence: affect the normal opening and closing of the valve and adjust the resistance, pressure and other functions. Even cause system operation, valve damage forced to repair. Measures: be familiar with the application scope of various valves, and select the specifications and models of valves according to the design requirements. The nominal pressure of the valve shall meet the requirements of system test pressure. According to the requirements of construction specification: stop valve shall be used when the diameter of water supply branch pipe is less than or equal to 50mm; gate valve shall be used when the diameter is greater than 50mm. Gate valve shall be used for hot water heating dry and vertical control valve, and butterfly valve shall not be used for fire pump suction pipe.


Taboo 4: wrong valve installation method. For example, the water (steam) flow direction of stop valve or check valve is opposite to the sign, the valve stem is installed downward, the check valve installed horizontally is installed vertically, the handle of rising stem gate valve or butterfly valve has no space for opening and closing, and the valve stem of concealed valve does not face the inspection valve. Consequence: valve failure, switch maintenance difficulties, stem down often cause water leakage. Measures: install in strict accordance with the valve installation instructions. The rising stem gate valve shall have enough stem extension opening height. The handle rotation space shall be fully considered for the butterfly valve. The stem of various valves shall not be lower than the horizontal position or downward. The concealed valve shall not only be provided with an inspection valve meeting the opening and closing requirements of the valve, but also the valve stem shall face the inspection valve.


Taboo 5: ordinary valve flange is used for butterfly valve flange. Consequence: the size of butterfly valve flange is different from that of common valve flange. Some of the inner diameter of the flange is small, while the valve disc of butterfly valve is large, which results in failure to open or hard opening and damages the valve. Measures: the flange plate shall be processed according to the actual size of butterfly valve flange.


Taboo 6: there are no reserved holes and embedded parts in the construction of the building structure, or the size of the reserved holes is too small and the embedded parts are not marked. Consequence: in the construction of warm and sanitary engineering, chiseling the building structure, even cutting the stressed steel bars, affects the safety performance of the building. Measures: be familiar with the construction drawings of the heating and sanitation project, actively and carefully cooperate with the construction of the building structure to reserve holes and embedded parts according to the needs of the installation of pipes and supports and hangers, and refer to the design requirements and construction specifications for details.


Taboo 7: during pipe welding, the staggered joint of pipes after butt joint is not on a central line, no gap is left for butt joint, no groove is cut for thick wall pipes, and the width and height of weld do not meet the requirements of construction specifications. Consequence: if the pipe is not in the same center line, it will directly affect the welding quality and appearance quality. No gap shall be left for butt joint, no groove shall be cut for thick wall pipe, and when the width and height of weld do not meet the requirements, the welding cannot meet the strength requirements. Measures: after the butt joint of the welded pipe, the pipe shall not be staggered. It shall be on a central line. The butt joint shall have a gap. The thick wall pipe shall be beveled. In addition, the width and height of the weld shall be welded according to the specification requirements.


Taboo 8: the pipeline is directly buried in frozen soil and untreated loose soil, and the spacing and position of pipeline buttresses are improper, even in the form of dry bricks. Consequence: the pipeline is damaged in the process of backfill compaction due to unstable support, resulting in rework and repair. Measures: the pipeline shall not be buried on frozen soil and untreated loose soil. The distance between buttresses shall meet the requirements of construction specifications, and the supporting pad shall be firm, especially at the pipeline interface, which shall not bear shear force. Brick buttresses shall be built with cement mortar to ensure integrity and firmness.


Taboo 9: the material of the expansion bolt for fixing the pipe support is poor, the hole diameter for installing the expansion bolt is too large or the expansion bolt is installed on the brick wall or even the light wall. Consequence: the pipe support is loose, the pipe is deformed or even falls off. Measures: qualified products must be selected for expansion bolts. If necessary, samples shall be taken for test and inspection. The hole diameter for installing expansion bolts shall not be greater than 2mm of the outer diameter of expansion bolts. Expansion bolts shall be applied to concrete structures.


Taboo 10: the strength of flange plate and gasket for pipeline connection is not enough, and the connecting bolt is short or the diameter is thin. Rubber pad for heat pipe, asbestos pad for cold water pipe and double pad