iMac is making my PING go very high.

[Tom2893]

Whenever my iMac is turned on and connected to the wifi, it makes our internets ping go to 200ms, instead of the usual 30ms. Why is this? It never used to do it..

We updated it to El capitan I think and its done it since then.
Help thanks

 

[Precursor]

Do you have a 802.11 ac router? One of the devices connected to your wifi is slowing the whole wifi network down. Try disconnecting all devices and connecting with your iMac only