This is where the investigation begins. Firstly, you have to identify if you have more than one pump in your hot tub. If you use more than one button to operate the jets then you probably do. If you open the service cover, you should be able to see exactly what you have.   If you have more than one pump, then the chances are you have a circulation pump as well as a jet pump or at least a pump that does the circulation too.   In general, a circulation pump will be the smaller of the two. You may have more than one pump as some larger hot tubs have three or even four pumps.   What you need to do is identify which is the circulation pump or if it is a dual speed pump, which pump is doing the water circulation.   This should be a case of turning on your hot tub and turning up the heat. There will only be one pump running at this point and this is the one that we will need to use to get water to your air source heat pump.   Drain the tub Now that we have identified which pump is used by the hot tub to heat the water, we now need to drain the tub.   Once we have emptied the hot tub, we are going to need to cut into the water lines of the hot tub so we can attach the Air Source Heat Pump.   As a general rule, you should be looking to cut into the water pipe just after your spa pack. If you are not sure what the spa pack is, this is the square box that has all the pumps, blowers and lights connected to it.   Trace your plumbing If you trace the plumbing, you should see that water from the lower drains comes into the front of the pump. Then, from the pump it will go into a filter, from the filter into your spa pack and then from your spa pack, it will go back into the jets in the tub.   If you have multiple pumps on your Hot Tub, one of them will follow this plumbing layout and that is the one we want to use.   What we are going to do is cut into the water lines after the spa pack to add the additional heat source which in our case is going to be the air source heat pump.   You will need to remove a 10cm/4” section of the pipe. You can use pipe cutters or a hand saw to do this. Be careful you do not catch any of the other pipework and put holes in anything! Last thing we want is leaks.   With a section of pipe removed, you now need to glue in with PVC Pipe Cement a couple of 90 degree 2” bends to be able to take your pipework outside of the tub over to your air source heat pump.   The chances are that you are going to need to cut holes in the exterior of the tub to allow the new pipework into the system so be mindful of this too.