A pitless adapter for use with a groundwater heat exchanger comprising: a casing comprising a first port a second port and a third port; and a spool removably received within an interior cavity of the casing, the spool including: a top plate; a bottom plate a first middle plate between the top and bottom plates; a second middle plate between the first middle plate and the bottom plate; a first port, a second port, and a third port in the bottom plate, wherein: the casing, the top plate and the first middle plate define a first chambe that is open to the first port of the casing and the first port of the spool; the casing, the first middle plate and the second middle plate define a second chamber that is open to the second port of the casing and the second port of the spool; the casing, the second middle plate and the bottom plate define a third chamber that is open to the third port of the casing and the third port of the spool; a first fluid pathway extends from the first port of the spool through the third chamber, the second middle plate, the second chamber, and the first middle plate to the first chamber; a second fluid pathway extends from the second port of the spool through the third chamber, and the second middle plate to the second chamber; and a third fluid pathway extends from the third port of the spool to the third chamber. a casing comprising a first port a second port and a third port; and a spool removably received within an interior cavity of the casing, the spool including: a top plate; a bottom plate a first middle plate between the top and bottom plates; a second middle plate between the first middle plate and the bottom plate; a first port, a second port, and a third port in the bottom plate, wherein: the casing, the top plate and the first middle plate define a first chambe that is open to the first port of the casing and the first port of the spool; the casing, the first middle plate and the second middle plate define a second chamber that is open to the second port of the casing and the second port of the spool; the casing, the second middle plate and the bottom plate define a third chamber that is open to the third port of the casing and the third port of the spool; a first fluid pathway extends from the first port of the spool through the third chamber, the second middle plate, the second chamber, and the first middle plate to the first chamber; a second fluid pathway extends from the second port of the spool through the third chamber, and the second middle plate to the second chamber; and a third fluid pathway extends from the third port of the spool to the third chamber. a top plate; a bottom plate a first middle plate between the top and bottom plates; a second middle plate between the first middle plate and the bottom plate; a first port, a second port, and a third port in the bottom plate, wherein: the casing, the top plate and the first middle plate define a first chambe that is open to the first port of the casing and the first port of the spool; the casing, the first middle plate and the second middle plate define a second chamber that is open to the second port of the casing and the second port of the spool; the casing, the second middle plate and the bottom plate define a third chamber that is open to the third port of the casing and the third port of the spool; a first fluid pathway extends from the first port of the spool through the third chamber, the second middle plate, the second chamber, and the first middle plate to the first chamber; a second fluid pathway extends from the second port of the spool through the third chamber, and the second middle plate to the second chamber; and a third fluid pathway extends from the third port of the spool to the third chamber. the casing, the top plate and the first middle plate define a first chambe that is open to the first port of the casing and the first port of the spool; the casing, the first middle plate and the second middle plate define a second chamber that is open to the second port of the casing and the second port of the spool; the casing, the second middle plate and the bottom plate define a third chamber that is open to the third port of the casing and the third port of the spool; a first fluid pathway extends from the first port of the spool through the third chamber, the second middle plate, the second chamber, and the first middle plate to the first chamber; a second fluid pathway extends from the second port of the spool through the third chamber, and the second middle plate to the second chamber; and a third fluid pathway extends from the third port of the spool to the third chamber.