How to use K-seal

Is that the blue bottle orange riding or orange bottle blue and orange riding on it anyway block sealers not a big fan Don't recommend personally but do what you think you have to do if you have a head gasket leak starting you're going to need to look at dealing with that engine problem these can be some weekends to the 2Z and you may want to look into that it's nothing personal it's just that's what you may be up against putting glue and sealers and fillers in your engine block is generally not the way to go Good luck my friend

 

Use k seal it will 100 burn your water pump in a few weeks

 

The safest way to use K-Seal is to pour it directly into a trashcan.
Do not dump it down the toilet since it is toxic to aquatic life, and keep it far away from the engine block since it will definitely clog up the heater core. Whatever the cost of a proper head gasket repair, the cost of undoing the damage caused by a stop-leak solution will always be more.

 

To answer your question while still not advocating a sealer, the Prius "reservoir" is part of the coolant circulation and has a pressure cap. So a sealant could be used there. If it were me, I would remove the cap and drive it slowly until the car was warmed up, maybe 5 minutes in hot weather and then add the sealant slowly ensuring it gets mixed well with the circulating coolant.

But the risks of heater core, radiator, coolant passage and thermostat clogs have to be high if the sealer can clog a high temperature high pressure cylinder head gasket leak.

With that said, people do it and sometimes get immediate relief, usually after symptoms are recognized but before fast coolant loss is apparent. If you do it, get the engine fixed as soon as possible in an effort to minimize further damage.

 

And then see if you can get that stuff out of all the passages.