I am not a huge fan of adding chemicals to a residential boiler. When adding chemicals to a steam boiler, it is essential to follow the manufacturer's instructions from the chemical and boiler manufacturers precisely. Not following these directions could change the pH of the water, causing more issues. Many steam boilers do not offer a good way to get the chemicals into the boiler, especially powders like Squick. Making this chore easier will mean considering this option during the installation process. I would suggest adding a tee and a plug to a boiler riser. Verify there is no steam pressure on the system, then remove the plug to allow the chemical to drop directly into the boiler. Fire up the boiler and allow it to warm up while circulating the chemical around the boiler. Below is the suggested piping on a single riser. If using a dual riser, choose either boiler riser to add the tee and plug for chemical addition.

Tee on a two riser and dropped header application

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