When the spa jets are on at the same time as the spa heater, the water comes out warm instead of hot. It's my guess that the water is coming from the cold pool instead of the spa. Any suggestions? Thank you.
Ideally, when in spa mode, the filter pump draws water from the spa and return the water to the spa. Provided the suction and discharge diverter valves are fully functional and positioned accordingly to circulate the water in the spa.
Typically, the spa jets have its own dedicated pump and a motor or motorless blower. When you turn on the jet pump on a heated spa, the blower sucks fresh air to create the venturi effect. Hence the bubbles! Therefore, it is normal for the water coming out of the jet to be cooler. Inspect the filter pump diverter valves if you’re in doubt.
Definitely verify that your valves are in proper position for SPA mode. It should have its own dedicated loop, suction from the drain in the spa to the pump, through the filter to the heater and return back to the spa via spa jets. Also, is your heater operating and set at a temperature higher than your water temperature? It will not kick on unless your pool temp. is lower then the heater set temp.
Thank you to both of you for your help. Yes, the heater is definitely on while the jets are going. I can feel some heat, just not very much. Our heater is 500 BTUs so when the jets aren't on but the heater is on, the water is so hot it would burn anyone inches from the return.
How would I know if it's plumbed correctly or the valves are in the proper position?
Maybe post a picture of your pump and valves that operate the spa. Show them in proper position to circulate the spa. If the valve handles are turned properly are you sure the actual valve turned - i.e. are the valves old or maybe not functioning? Can you put your hand on the exit piping of the heater - is it warm? Is the exhaust of the heater hot? The operation entails several items that need to be verified.
Is the plumbing for the flow path correct to warm the spa?
Are the valves in the flow path working properly such that you know the flow path is correct?
Is the heater working?
Do you have electricity or gas to the heater?
Keep us informed of your progress.