You will need to check where it is installed and compare that to the model number of the heater. A vacuum heater must be installed in front of the pump on the suction line coming from the suction cover inside the bathtub. If you have a WOW pump then that style of heater will not work in the suction line because the pump doesn't have enough '****' to operate the vacuum switch. A pressure heater is installed in the pvc piping after the discharge of the pump. anywhere in that line before a the jets.
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You will need to check where it is installed and compare that to the model number of the heater. A vacuum heater must be installed in front of the pump on the suction line coming from the suction cover inside the bathtub. If you have a WOW pump then that style of heater will not work in the suction line because the pump doesn't have enough '****' to operate the vacuum switch.
A pressure heater is installed in the pvc piping after the discharge of the pump. anywhere in that line before a the jets.