（法律問題）租客不交租，可否斷電斷水？

It depends on the circumstance.

Discontinuing water supply and electricity is not illegal per se. Under Hong Kong Ordinance Chapter 7 (Landlord and Tenant (Consolidation) Ordinance) Section 45:

"(1) 任何人惡意作出任何作為，意圖誘使處所的承租人捨棄對處所的管有，循簡易程序定罪後，可處罰款$2000。

(2) 在聆訊根據本條發出傳票的案件時，裁判官除可判被定罪的被告人罰款外，並可命令被告人付給承租人一筆款項，其數額使裁判官覺得足以賠償承租人因被告人的作為而蒙受的費用、損害、損失或不便。"

If the rent payment does not include utility (water/electricity), of course you have no right to discontinue anything.

However - if the rent payment includes utility, and the tenant(s) fails to pay after a reasonable time (like after the grace period), the landlord in fact has the right to discontinue the utility based on the fact that the tenant's bad faith in breaching the contract.

You can see here for more detail:

http://www.eaa.org.hk/Home/Publications/MonographHongKongDomesticTenancy/3ContentsofaTenancyAgreement/tabid/419/language/zh-HK/Default.aspx

租客遲交租與欠租是兩回事，長期欠租可用法律情序收樓，但經常遲交租的是耐租客不何的，只能等到租約期滿不予續約；斷水斷電是滋擾行為屬刑事違法，業主應謹慎處理，避免追租不成反而惹上官非。