Question:
We are adding on two new baths(one up and one down), we are going with a gas water heater, would we benefit from adding an recirculating pump?
By benefit, I mean:
Is it economical?
Will it save wasted water?
Is it really worth the added costs to have fairly instant hot water?
I hope I added enough information
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“Have you seen my baseball?”
Replies
I've always wondered the same thing. With re-circulating pumps, you have the cost to run the pumps, plus you in effect increasing the size of your water heater to maintain water temperature in a poorly insulated container (your hot water supply pipes).
>> ... to maintain water temperature in a poorly insulated container ...No reason why the pipes would have to be poorly insulated.
If you are adding the baths, and it's feasible, consider running a 'gravity' loop back to the hot water tank. It uses no energy other than the heat loss through the recirculating lines. And there isn't much that can go wrong with it!
If you are like us and used to brush your teeth waiting for the upstairs bath to get hot water, the loss of line cooling will be minimal compared to the loss of water running that long to get hot.
Let's not confuse the issue with facts!
i like he gravity idea.
i did fail to mention its a tankless gas heater.
we are keeping our electric tank, but it will be used for the existing house, and it will be fed hw from the gas tankless.
hmmmm possibilities-----------------------------------------------------------------------------
"Have you seen my baseball?"
You can use your existing electric heater as a storage tank for the tankless heater, but adding a circulating loop on top of that is getting into NASA territory in terms of valves and complexity. Heat loss is much lower than with gas heaters as most electric tanks are well insulated and don't have a flue that will allow heat to escape.There are four connections on a typical electric heater. You will use one for the inlet, one for the hot water out, and the other two for the loop to the tankless heater. Since one of these connections will eliminate the tank drain fitting, you need to provide a drain in your added plumbing. The same is true for the pressure relief valve - it will have to be put on the end of a tee. The tank thermostat can be used to switch on the circulator pump whenever the water temmperature in the tank drops below the set point, and it will run water through the tankless unit until it reaches the hot set point. Unless you are familiar with this type of work, you probably should get a good plumber on it. Here is a web page with a diagram that will give you some ideas for where to start:http://tinyurl.com/dp9uf
The tradeoff is water vs. energy.
A far flung outlet will waste a gazillion gallons of water over the long run, and is inconvenient.
Even a well-insulated recirc loop will have greater net standby heat losses than with no recirc system, but these losses can be lessened by using a pump with a timer and a thermostat. (see Grundfos UP series; http://www.grundfos.com/web/homeca.nsf/Webopslag/A22F3089EB72820985256AFD0077136F). Of course, if you live in a cold climate, standby losses do not really count during the heating season, and the electricity used does not amount to much at all.
A gravity recirc system uses no electricity (and has just 1 moving part), but lacking the timer and thermostat, it will generally consume more net energy.
The 3rd recirc option is an 'on demand system'. When you want hot water, you first activate (via a switch) the recirc pump, then wait a few seconds before claiming your hot water. This is somewhat more expensive to buy, and more labor to install. (see Metlund; http://gothotwater.com/)