電熱水爐 ?

--would it be the cold water arrive to the sink before the hot water does?
if you has a value that control the cold water to the sink (usually locate under
the sink), you can adjust that value a little bit to see if it solve your problem

在家裡有一些水喉總掣或分掣, 你可先自行調較大小流量; 相信會有幫助.

叫電氣技工檢查索掣
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