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The most commonly used compensators in hot water systems include: sleeve expansion joints, bellows compensators, and rubber joints. Natural compensation makes use of the L-shaped or Z-shaped turns formed during pipeline layout to serve as a compensating mechanism. However, this amount of compensation is very small; as the pipeline expands and contracts, it undergoes lateral displacement, which causes significant stress on the pipeline. It is suitable for situations where the straight length of the pipeline is short and there are many turns; for steel pipes, the general straight length should not exceed 20 meters, while for copper pipes it should not exceed 10 meters. The sleeve expansion joint has a large expansion range, occupies little space, is easy to install, and presents low fluid resistance; however, it is prone to leakage and requires frequent maintenance as well as replacement of the packing. It should be installed on straight pipe sections, with fixed supports at both ends to ensure that the pipe can expand and contract freely without any lateral displacement. A bellows compensator is made of a thin-walled, highly elastic material with annular corrugations along its axis; it can undergo axial tension and compression movements as well as lateral or bending deformations. There are various types of bellows compensators, and their applicable conditions should be taken into consideration when selecting them. Internal pressure axial compensator: Suitable for compensating for thermal expansion and contraction in thermal pipelines, or for compensating for high-frequency vibrations. Jacketed axial compensator: Suitable when the compensator requires external insulation and needs a large amount of axial compensation. Double-acting axial compensator: It provides a large amount of expansion/contraction compensation, which can exceed twice that of the internal pressure type. External pressure axial compensator: In addition to the advantages mentioned above, it is equipped with exhaust and drain ports that allow for the removal of any residual liquid in the compensator’s interior. Universal compensator: Can compensate for large lateral displacements and bending deformations. Metal flexible hose: It consists of a connector, a bellows body, and a mesh sleeve. It features good bendability, as well as resistance to high and low temperatures and high pressure. When the hose is in use while bent, its bending radius should be no less than 10 to 20 times the diameter of the hose.