According to Matsyapurāṇa (Matsyapurana) Āpavatsa (Apavatsa) is one of those gods whom one needs to worship during the foundation of the base of a new palace.
It is said in Matsyapurāṇa (Matsyapurana) that Āpavatsa has to be offered dadhi (curd) as naivedya (food-offering).