Yes. And it depends on how long you let it be. Plasticizers are tiny particles which leech out of the tubing and float into the fluid and around your loop. If they get caught somewhere (or group up and get caught somewhere), they can start to reduce flow and eventually block it. If you want to use cheaper tubing, then you probably want to be cleaning your loop (which includes cleaning components) a lot more frequently than if you buy more expensive stuff.