Tanks to accept blowdown from a steam boiler should be designed to meet the task. Simply, per the National Board who recommends safe practices based on experience and technical design, the tanks should be built per ASME design standards and plated to state pressure rating and temperature as well as other needed details of operation limits. Tanks can be of closed or open design. Code states that condensate and materials in tanks should not be released to drains until under 140F. Reimers makes tanks that meet ASME design, have controls on them to allow safe operation and prevent release of condensate when above 140F.