According to the results of the housing situation survey by the Ministry of Land, Infrastructure and Transport, more than half of the housing types in Korea, such as apartments, have already been built, and it is expected that the number of housing will continue to increase in the future. Multiple accidents can occur in multi-unit dwellings, and in many cases, damage to the lower floors is caused by leaks caused by pipe damage in buildings. By the way, in the case of renting an apartment building, many disputes arise over who is responsible for the cost of repairs between the lessor and the lessee. In this paper, we have been discussed who is responsible for damages according to such a rental relationship, and how far is the scope of compensation. In addition, since leakage accidents are closely related to our lives and occur frequently in our surroundings, insurance products that cover them are sold. For who lives in residential housing (apartments, multi-family houses, etc.) are allowed to subscribe ‘daily (family) life liability insurance’, and for stores or business buildings other than private homes, are applicable for ‘Premised & Operations Liability’. When accident of water leakage occurs, the cause of the leakage is detected and the leakage points are repaired, and finally restoring the damage on the lower floor. Repair costs for restoration include the repair cost of the leak point and the repair cost of the damaged household. Damaged household is applicable for a third party liability, so restoration of original state is the standard. Contrary to this, there were many disagreement regarding the compensation for the repair cost of the insured's home, and each insurance company had different compensation standards. On June 15, 2013, the Financial Supervisory Service Dispute Mediation Committee recognized the repair cost of the leak point as the cost of removing the cause and judged it as ‘expenses for fulfilling the Duty to Prevent Loss’. There has not been a Supreme Court decision yet, and each district court has different conclusions about ‘expenses for fulfilling the Duty to Prevent Loss’. In 2018, the Seoul Southern District Court ruled that the cost of repairing the leaking point as ‘sue and labor charges’, and in 2019, the Gwang-ju District Court and the Seoul Eastern District Court ruled that it was not ‘sue and labor charges’. And on July 08, 2020, the Financial Supervisory Service's Dispute Mediation Committee reconfirmed that the repair cost of the insured's home leak point should be paid as ‘Duty to Prevent Loss’. Since the payment of insurance money is linked to an increase in insurance premiums, there must be a reasonable payment standard. It is difficult to distinguish the reason of repairing points whether it is caused by deterioration or due to leakage of water. In addition, since the duty to reduce damage to prevent damage under the Commercial Act is an obligation that arises after an insurance accident occurs, the cost of repairing a leak point in one's house cannot be included in the cost of damage prevention due to the nature of the log, and it is far from the purpose of acknowledging the duty to reduce damage prevention in the law. Due to the recent advancement of building materials, etc., the repair cost of a leak accident is gradually increasing, and there are many cases where the repair cost at the leak point is higher than the damaged household. In this regard, I wrote opinions based on accident cases whether the ‘Expense for Fulfilling the Duty to Prevent Loss’ can be recognized as the repair cost of the leak point. In addition, in order to guarantee risk to such a level, it is proposed to develop and utilize a special contract terms to subdivide risks and comply with the ‘principle of risk homogeneity’ or the ‘principle of equal treatment of policyholders’. It is expected that the correct interpretation of insurance terms and conditions and reasonable compensation standards will be established in relation to leakage accidents that occur frequently around us.