Push in fittings are a popular alternative to traditional fittings and are suited for plumbing systems such as potable water, hydronic heating systems, irrigation, and water heaters. No specialist tools are required and they're much quicker to fit than other fittings. Just push the tube into the fitting to create a strong seal. These Push In Y Unions are used to connect tubes in a straight line set up either combining 2 flows into 1 or splitting 1 flow into 2.