Hot Water Recirculation Choices
If it's not too expensive, I want to install a recirculation system for the master bathroom of our remodel, which is about a 45' pipe run from the water heater. I estimate we would have to wait about 35 seconds without recirculation before hot water would appear. (Kitchen and downstairs bath are very close to the heater.) Pipe is 3/4" L copper. I'd like to not waste water or have to wait a long time for hot water to appear, but I also don't want to pay for something that would take 10 years to recoup the cost.
There are 2 choices which are intriguing to me.
1. Gravity fed convection system. This should work since the water heater will sit in a utility closet at ground level, first floor is 2 feet higher above a crawl space, and master bath is on second floor. My understanding is that we need a 3/4" return line from upstairs with the whole loop insulated EXCEPT for 15-20' at the end of the return line (just before the water heater), and that this cooler section is what sets up the convection flow–albeit a slow flow, which I assume is good. If this doesn't work, it may be necessary to install a check valve going into the drain side of the water heater, and if THAT doesn't work, can I assume that a recirculation pump can be installed retroactively? My contractor is not experienced with gravity-fed systems.
2. Contractor recommends a (new) product that he has used in his last 3 houses. It uses a pump but does not require the installation of a return line. Somehow, the hot water at the end of the line trickles into the cold water side. Does anyone know what this product is and what might be the pros and cons?
I'm installing a Grundfos today
I'm actually installing a GrundFos Comfort Series pump today. I'm actually doing it not for instant hot water, but to stop some very inaccessible pipes from freezing (slight circulation of hot water should prevent freezing, that's the idea anyway). I bought mine new on **** for $175 which was much cheaper than I could find from a plumbing supply store.
Installing it seems to be a snap. It connects right above your water heater on the hot side. On the bottom of the pump is a connector to attach to the 3/4" male on the water heater. At the top of the pump is a 3/4" male. I have 3/4 copper into my heater, so I had to cut about 6" off, sweat a 3/4 female and I was done with pump install. Now, I'm installing the comfort valve on my bathroom faucet which should be very easy.
Taking a lunch break right now, or I'd be done. If you're interested, I'll try to get back to you with a report on how it works. BTW, there's a couple threads from a couple months ago about this topic.
Hot water circulation; control vs open thermostatic valves
A closer look at thermostatic recirculation systems, particularly thermostatic valve operations, appear to validate homeowners disappointments of waiting for cold water and abnormally high gas bills, conveyed by nearly 100 professionals interviewed at the 2006 Southern California Annual PHCC trade show. Thermostatic valves connect the homes hot and cold water lines together and the internal valve opens and closes in reaction to the hot / cold water contacting them. These normally open valves constantly remain open unless 95F degree water or hotter constantly contacts them to keep the valve closed. To prevent inefficient hot water line siphoning through these valves would require homeowners to constantly maintain hot water throughout their homes hot water pipes 24 hours a day.
Any use of cold water, i.e., flushing toilet, indoor/outdoor watering, icemaker refills, etc. which drops the water pressure in the cold water line while the thermostatic valve is OPEN, causes any <95F degree water in the hot water line to rapidly pass through the open valve and into the cold water line. Resulting in additional energy consumption by the water heater to heat the cold city water which entered the water heater to replace the water which passed through the open thermostatic valve, even though only cold water was used by the homeowner. This inefficiency can result in users having to wait for cold water from their faucets for tasks which warm water is less then ideal, even unacceptable, i.e., taking vitamins/pills, brushing teeth, washing off fruit / vegetables, salad prep, filling pitchers/drinks, recipes, watering plants, etc. Depending on the distance to the water heater, a home owner could wait quite a while before water hot enough to close the valve arrives from the water heater. Read more at http://www.redytemp.com/comfort_valv...et_install.htm
Recirculation pump Demand-sensing controller
Residential Demand-Sensing Hot Water Recirculation System
A recirculation pump with a dedicated return line and a timer has two problems:
1) Most of the time the pump is running, it is not needed
2) when Hot water is needed, the pump is often not running.
I solved the problem with a unique "on-demand" control that turns on the pump when the hot water anywhere in the house is turned on.
Here is a diagram of the system:
1) On the cold water IN on the Hot Water tank, a flow switch is installed that turns on when it detects flow. (Note: This can *not* be anywhere in the circulation loop)
2) A Delay-Off timer turns the pump on immediately when the Flow Switch turns on, but does not turn off the pump for a while after the flow switch is turned off. (The delay time needs to be adjusted for the characteristics of the particular installation. Typical times range from 30-90 seconds)
3) An aquastat is used to turn off the pump when the farthest faucet in the loop reaches temp.
When the hot water is turned on, the pump comes on and hot water arrives fairly quickly (but not instantly). The innovation is this: Turn the hot water on for a second and then turn it back off...and the pump keeps going for a while. Then just wait for a little bit and turn the Hot water back on...it is hot and ready to use. However, after the water is turned off, the pump will run for the delay time and then stops till the next time there is demand.
Parts that I used to build the control circuit:
Flow Switch: Gems 26615 (I got it cheap on a bidding site). (http://www.gemssensors.com/Applicati...nQuestionID=36 ) Others are available, but be sure to get one that has a fairly low trip point on the flow. (.75 – 1 GPM)
Delay off Timer: MX046 timer kit. (15 second to 6 min delay)
(http://www.bakatronics.com/shop/item.aspx?itemid=466) It is inexpensive but you must build it into a case. There are other delay-off timers and relays available but this seems to be the cheapest option.
Aquastat: Grundfos 1/2" Clip-on Control 115 volts #595443.
(http://store.waterpumpsupply.com/aqhotwattemc.html) Get the ¾ inch if that is what you need for your pipes.