Use FAILOVER servers!!!
This may help - https://eth.nanopool.org/help
Nanopool URL failover servers (port are the same for all - 9999):
Europe:
eth-eu1.nanopool.org
eth-eu2.nanopool.org
USA:
eth-us-east1.nanopool.org
eth-us-west1.nanopool.org
Asia:
eth-asia1.nanopool.org
Japan:
eth-jp1.nanopool.org
AUstralia:
eth-au1.nanopool.org
Check servers for fastest ping and use 3 or 4 of them