Clean blockages without damaging your pipes! As a rule of thumb, the amount of pressure loss, will match up to the water loss and, this water needs to go somewhere; hopefully not on your carpet. Use one part caustic soda for every four parts of water. Or, if you're looking to save even more cash, why not take on our. Gas-fired wall-mounted condensing boiler with modulating stainless steel cylinder burner and inox-radial heat exchanger surface rated input: to mbh for residential homes and.