The pool's hot wallet addresses are:
This wallet maintains the magnitude, receives the proof of research awards, and interest payments.
Also the wallet handles the payouts to pool members.
If you send coins to the hot wallet, you will effectively "rain" coins on the hosts in the pool.
This is because payout amount is determined based on the wallet balance, minus the basis and interest
Also any project rain received into the hot wallet will be distributed to the hosts in the pool regardless of the project they are crunching on.