Because I lack so much data his is almost impossible to calculate, but I'd like some best guestimates.
I'm trying figure the cost difference between wasting 4.2 gallons of water that will need to be replaced and reheated, paid for and paid again to dispose down the sewer, vs heating and recirculating water.
I have calculated that 3 showers a day, wasting 1.4 gallons each time before we get hot water, for a total of 4.2 gallons. The cost to heat the water plus the cost of the water and the cost of the sewer is $0.25 per day.
Now the question is how much water do I need to recirculate each day to keep the water hot at the bathrooms. (i.e. how much extra water will I need to reheat each day because of the water that cools in the pipes before recirculation.? I expect to run the pump 15 hrs a day, but it will only flow water when the faucet has cooled to 90*F
The two bathrooms are at the opposite end from the water heater. That's 40 ft of 1/2" copper pipe in/under a concrete slab in Fl. that fills and
cools before recirculating. That calculates to 0.9 gallons of water to heat each time the water cools to 89*F. I could heat about 7 or 8 gallons of water for the cost of the wasted 4.2 gallons of water used without the recirculating pump.
How many times do you think the valve cycles in a 15 hour day? The cost benefit gets better when I start adding in the use from the kitchen sink, but I don't have a number for how often we wait for hot water and how much water flows while waiting.
This all seemed to be for my clarification and edification, but if you have any incite about this, please post.
BTW, my electricity cost is about 17cents per kWh and my water with sewer cost is 2.4 cents a gallon.
Qmavam.
I'm trying figure the cost difference between wasting 4.2 gallons of water that will need to be replaced and reheated, paid for and paid again to dispose down the sewer, vs heating and recirculating water.
I have calculated that 3 showers a day, wasting 1.4 gallons each time before we get hot water, for a total of 4.2 gallons. The cost to heat the water plus the cost of the water and the cost of the sewer is $0.25 per day.
Now the question is how much water do I need to recirculate each day to keep the water hot at the bathrooms. (i.e. how much extra water will I need to reheat each day because of the water that cools in the pipes before recirculation.? I expect to run the pump 15 hrs a day, but it will only flow water when the faucet has cooled to 90*F
The two bathrooms are at the opposite end from the water heater. That's 40 ft of 1/2" copper pipe in/under a concrete slab in Fl. that fills and
cools before recirculating. That calculates to 0.9 gallons of water to heat each time the water cools to 89*F. I could heat about 7 or 8 gallons of water for the cost of the wasted 4.2 gallons of water used without the recirculating pump.
How many times do you think the valve cycles in a 15 hour day? The cost benefit gets better when I start adding in the use from the kitchen sink, but I don't have a number for how often we wait for hot water and how much water flows while waiting.
This all seemed to be for my clarification and edification, but if you have any incite about this, please post.
BTW, my electricity cost is about 17cents per kWh and my water with sewer cost is 2.4 cents a gallon.
Qmavam.