Best Hot water recirc for new construction?

Nate,

You might want to chat up Ray Moore here on PC. Sounds like he might have some experience with that sort of thing.

 

I'll ask a plumber buddy of mine. If you don't get an answer soon, i'll get ya one. I'm not exactly sure what's required myself and i've done general contractor work... but mostly after build. add rooms.. landscape.. etc.

 

This is not quite what you want, I think. But I've been exploring this for my house. The problem is that I would need a pump because my shower is on the 1st floor.

Try this site. It's not for recycling the hot water, but to recycle the heat in that water:

http://www.gfxtechnology.com/

http://www.renewableenergyworks.com/products/gfx/gfx.html


This device really only works to recover the heat from shower water. It does not work for any single use of hot water, like the bath or clothes washer.

It also works best if the shower is on the upper floor. However, I've read that it will also give you more energy than you will take even when you use a pump.

 

Nate,
Don't know how good they are, but this is the product I've been looking at. http://www.gothotwater.com/
Lewis

 

I re-plumbed my house with pex tubing with a centralized manifold system (Vanguard). Each fixture has its own dedicated line running back to the manifold, which, inturn, is fed from the water heater(about 3 feet away). Fixtures like toilets, and sinks use 3/8'' pex while tubs use 1/2''.

The nice thing about this system is the hot water is almost instantaneous, especially with the 3/8'' lines (no need for recirculation).

Advantages:
1) No pressure drops, ie; someone flushes the toilet while taking a shower.
2) Very quick hot water response.
3) No pipe noise while the water is running.
4) Each fixture can be isolated at the manifold.
5) No joints between the manifold and the fixture.
6) Color coded piping (blue for cold, red for hot).

 

Thanks for the info - I've been looking at solar and geothermal technologies for my next project. This will fit in well with both systems.

 

Not sure if this is what you were looking for, but we were considering this for our master bath which is on the opposite end of the house from our hot water heater:

http://www.chilipepperapp.com/ps.htm

It's kind of pricey, though.

 

Ask over at this site.

http://www.terrylove.com/

They really know their stuff.

I retrofitted a small pump (Home Depot stocks them) under the sink in the bathroom and it works quite well for those of you that want to recirculate hot water in an existing house.

 

naterprius-
I can help you out with this. It's more than I want to type right now but if you PM me I'll give you my phone number. I put in alot of them. You should know that they are not energy efficient systems and if not done well, they can really suck alot of energy.

 

I'd be curious as to what you decide - since I was considering one of these! Thanks!

 

That's pretty typical in my experience (I work for a heating appliance company, and we sell them, so I'm really talking "against" one of my own products). It actually works well for a vacation home type of thing, but for a house where you use a lot of hot water ... especially filling a bathtub from time to time ... the on-demand systems can leave a bit to be desired. The term "instantaneous" is one the industry is trying to shake right now, because it gives the consumer the wrong impression. There is still a column of cold water in the pipe that has to be discharged out the faucet, and the heater doesn't actually come on until the water starts to flow. But, the advantage is that the column of cold water could be less if the on-demand heater is located closer to the faucet.

Tank type water heaters start at about 82 - 84% efficient, and lose efficiency as sediment insulates the bottom of the heater (that's the crackling and popping you hear on older water heaters). Newer heaters try to minimize that by incorporating water-swirling devices so that the incoming water keeps everything in suspension, and they work pretty well.

A hot water recirc system typically takes the hot water from the farthest point in the house and pipes it back to the bottom of the hot water tank using a very small pump (most run continuously, but there are some that use a button you push a couple of minutes before using the hot water). If the hot water pipes are well insulated, all you've done is increase the hot water storage by the amount of the water held in the pipe, which is constantly recirculated. If the pipes are not well insulated, then you waste energy by radiating the heat out of the hot water tanks as it circulates. The advantage of a well insulated hot water recirc system is that you don't waste the heat in the hot water pipe from the tank to the faucet every time you turn off the hot water (that column of hot water cools off eventually).

 

There is no energy advantage in a well insulated recirc system. The insulation reduces the losses but they are still significant. The BTU losses can be figured using the length of pipe and number of elbows, the R-value of the insulation, the temperature of the water and the air temperature of the air around it, the efficiency of the water heater, and the velocity of the water flow. The losses will be greater depending on the deltaT (temperature differential), length of recirc line, amount of insulation, amount of flow and the heater efficiency.

When the water is maintained at a high temperature, the BTU losses are greater than when it is allowed to cool in the line between uses. The only savings are in the amount of water used.

My system uses a timer and a highly efficient Rinnai tankless water heater. While in operation, the pump uses 130 watts. The BTU losses have been calculated to be about 2000 BTUs per hour with my system. I use 1" wall insulation, 3/4" copper line, and a Taco 009 pump. With the propane that I use, that comes to 4 cents per hour at current prices.

All totalled the cost is about 5 cents per hour. For that reason and because we dislike wasting energy, we use a timer that runs the pump for 3 hours in the morning and 4 hours at night. We often override the timer and usually only run the pump about 3 hours per day. We find this to be convenient overall.

The upside is that we are able to use one efficient tankless heater in a large spread out home without waiting 40 seconds for hot water to get to the faucet. Multiple water heaters use more resources and take up more space. We save some energy by filling our dishwasher with hot water instead of water that has cooled in the pipe. This reduces the energy used by the dishwasher to heat the water internally and shortens run times.

This is a lifestyle choice. It is not a "green" choice. It can be done in a way to reduce the energy penalty but in the end, you are spending a substantial amount of energy for convenience.

These systems are plumbed in a big loop. If you don't run the pump, some fixtures will take substantially longer to get hot water than if all fixtures were plumbed by the shortest path to the heater. This means that the choice you make today will commit you for as long as the home exists to using the pump. It is not for everyone.

One final note on the energy losses. In the winter, assuming the recirc line is within the conditioned space, the thermal losses will contribute the heating of the home. In the summer, these losses will add to the cooling load.

There is more to consider regarding this issue but this will hopefully help get you started in making your decision.

Oh and by the way, 3/8" wall insulation is totally inadequate. Plumbers will tell you that the 1" is too expensive and not worth it and will balk at mitering the elbows and sealing all the joints. I have to work very hard to get them to do an acceptable job of installing these systems. There are a few technical issues to address as well such as check valves, expansion tanks, air bleeders, and anti thermal syphon loops.

Aren't you glad you asked?

Gotta go now.

 

I installed one of these about 5 years ago. Would never consider anything else again. They are a lifetime heater, anything that should go bad can be replaced as a piece part. You no longer have this huge tank eating up floor space, and you have an unlimited supply of hot water. Our water heating bill has dropped by about 1/3 with the tankless as well

 

When I had my last house built I simply told the contractor that I wanted recirculating hot water. The hot water heater was on one end of the house and the kitchen on the other. He plumbed in a simple pump that plugged in next to the hot water heater. Also, he told me to unplug the pump if water pressure was lost. I was on a shared well that had problems maybe once a year. Fortunately, I was at home each time this happened and ultimately, remembered to unplug the pump in each instance. Sometimes though I found the pump moter to be very hot by the time I did the unplugging. If I had it to do over again I would have placed a switch in the circuit. Better yet, a water sensing switch that would automatically turn the pump off with a loss of pressure (I'll bet it would cost less than one pump replacement visit from plumber).

A couple more points:

. I read an article recently that states that a recirculating pump is overall an energy saver.

. I like the idea of the timer (seems to me it would be no more expensive than a yard drip system timer circuit (cheap).

. At retirement I moved into this smaller home. My biggest gripe is waiting for the water to heat when I want to wash my hands, take a shower, or do the dishes. It just seems ludicrous to stand there and watch all that precious water draining down to the sewer. What a waste.

 

My sense from reading the web site, and from reading some excellent posts above, that it's at the very least cumbersome to make this system ENERGY efficient. And it would take some forethought every time you used the hot water.

What this system seems designed to do is less to save energy, and more to save water. Which seems to be exactly what Naterprius wants.

Someday I suspect systems like this will be required by code for cities built in the desert, like LA. But before they become workable they need to be less cumbersome. The push button would not work with the MTV generation.

One way to make them less cumbersome is to not make the water user have to press a button before wanting water, nor having the system constantly circulating that hot water. The switch could be built into the faucet handle. When you turn on the hot water, you get nothing but the pump starting. It could also not allow cold water either, until that hot water arrives, at least in the shower.

Nothing will come out of that spigot until the pump senses the hot water has arrived, and then the pump shuts off and redirects the water to the spigot. Such a system would definitely save water, and with properly insulated pipes, might save energy too.

And it would not require any forethought on the part of the water user.

 

Easiest, low-cost, low-maintenance method . .

Lay out the floorplan so the fixtures are all clustered near the water heater. I did and I get quick hot water at every fixture.

Also, use a well insulated hot water tank. I have 10 years of excellent performance from my Marathon unit and it's R-25 jacket. Marathon Water Heater

I also use solar water heating, which supplies over 90% of my hot water.

See my house and some energy tips at The Westbrook House. It's slanted for a North Texas hot climate.