how do i determine how many hot water loops I have in my home? i plan on installing a hot water circulation pump.

It all depends on how your home is plumbed. Normally you install the circulation valve under the sink that is farthermost from your water heater. With two floors at least one farthermost on each floor. This device works best when the plumbing is in a loop, but most homes have manifold plumbing, and thus the more sinks you have the circulation valve installed the faster that sink has hot water.

You'll need to install a sensor on the downstairs faucet furthest from your water heater and the same upstairs, so have an extra sensor ready before you start your install. Some times you will find upstairs that another faucet still runs cold water for too long after installation. This means the upstairs plumbing was split before it went upstairs and you'll need to add another sensor under that faucet as well. You can find additional sensors for as low as $40 if you search online. The nice thing with this pump is that you can always add more sensors in the future where needed and it won't prevent the system from working elsewhere in the house immediately.

Typically you would install at the farthermost point from the hot water heater. To test turn on the water at the sink you are considering installing a valve/sensor at and turn it off once you get warm water. Then go to another sink and turn the water on, you should see a reduced time to warm up. If the water still takes a while to warm up at the other sinks you may need additional valves.

If you have a crawl space, you need to start where the hot water line starts under the house from the heater and start mapping it out. If you have a crawl space and it's a two story house, you most likely have two loops with one feeding the second floor. You should be safe putting the one "smart valve" under the upstairs lavatory in the bathroom that is furthest from the heater because the main hot line would have to pass each branch that tees off to the fixtures in between. You can find the furthest on the loop also by timing how long each fixture takes to get hot water. But you have to let the lines cool in between testing and that takes a long time. I recommend definitely using the hot water circulation pumps that use a "smart valve" with the existing plumbing instead of running a loop from the furthest fixture like you have to do with the older style circulation systems. That way you can add as many "smart valves" as you need. Start with one and if you still have to wait for water in another part of the house, you can put another valve in that area too.

Unless you have blueprints of the property it is difficult to tell how many loops (home run system) you have. One method is to see how quickly hot water is at the furthers sink, then go to a closer sink and see if it takes just as long. Usually, in a manifold system where each sink is on it's own loop the hot water takes just as long for the second sink as it did for the first sink (beginning from the furthest away and then the next furthest). In a single loop system (one long loop through the house with T's off of the loop to each sink), once hot water is to the furthest sink, then the next furthest sink will get hot almost with 2 or 3 seconds. The principal of multiple loops is that the whole house system does not have to circulate hot water in order to get hot at one sink. The manifold limits the water flow to just the sink that is turned on. If you have a manifold system so each sink is on it's own loop, you'll need to buy the circulation pump's sensor at each sink that you want "instant hot". If it is a single loop for the whole house, generally one sensor will do it at the furthest sink; with the exception of some systems where one sink is a long ways away from the other sinks in the house. Don't buy the extra sensors until you know which sinks (if any) do not get hot water quickly. The last I checked the sensors run about $40. Good luck Mark