Utilities Reduction Project Part II: Water heating (nat. gas)

[Shawn Clark]

Continuing on in the series, I targeted reduction of my water heating costs. This project went hand-in-hand with water use reduction.

Determining the annual use requires a bit of estimating as only the summer months are on an apples-to-apples basis. Winter includes gas furnace use. So I have to use summer values then apply a factor because of the cooler incoming water in winter (this is a double whammy for shower calculations.) My current estimate is that my water heating duty will increase 50% for the coldest half of the year relative to the hottest half. The fixed storage losses change little because of the location of my water heater and lines.

During summer/early fall of 2008 we used 18.3 ccF nat gas/month. Roughly 5 ccF/month of this was storage losses before I insulated the tank and piping. So incremental heating for use was about 13 ccF/month in summer, and about 19 ccF/month in winter (add ~5 ccF/month storage losses to each.) This works out to an annual value of around 260 ccF/year. That is nearly spot on with Energy Guide value of 258 ccF/year for this model for "2.6 occupants."

By early Septemper of 2009 I had completed most of my water heating energy reduction projects. This yielded a 3 month average of about 11 ccF/month. Of that ~3 ccF/month was measured as storage loss. This means that our summer water heating is about 8 ccF incremental, and that our winter incremental would be about 12 ccF/month for an annual use of 156 ccF/year. A 40% reduction is not too shabby.

There were roughly four components to the reduction:

1. Blanket water heater/insulate lines. Last fall and winter I insulated the hot water lines from the heater to each fixture where I could reach them (perhaps 75% of the total linear feet.) I also have insulated the incoming water line near the heater to reduce thermosiphon, and I've insulated the relief valve and overlfow pipe. Finally I put an R6.7 blanket on the tank (wanted R10 but the stores were all out of them at the time...probably okay as the R6.7 was a tighter than expected fit. Together these may have been worth as much as 24 ccF/year.

2. Front loading clothes washer. In February I purchased a front loading washer. While only about half our loads are in warm water, and the mix for warm is about 50/50, the reduction is worth about 17 ccF/year.

3. Ultra low flow shower heads. The biggest impact was going to lower flow showerheads in all three showers. This was only fully completed in the last month. The 2.5 gpm showerheads I was using before tested out at about 2.3 gpm and the ones I have now come in at ~1.5 gpm. This is probably worth more than 50 ccF nat. gas/year for us. I plan to update reviews for the showerheads I've tested, there were some surprising results.

4. Being more cognizant of hot water draws/reducing short draws. It's hard to put a value on this but we've become more aware of our hot water draws, particularly in the distant kitchen (a run that is mostly uninsulated) so that we can bundle uses while the lines are still hot. It's analogous to combining trips in the car. I've started using cold water more for quick rinses of clinging food. I also wait to run the dishwasher when the lines are already hot.

Since we already have an Energy Star dishwasher there is no low hanging fruit left. More radical changes are needed to squeeze out more, such as a condensing tank water heater, tankless water heater, or solar. Drainwater heat recovery might be possible in our master bath shower, but I doubt it would net more than 30 ccF/year and it would consume much of a handy storage space.

[patsparks]

I'd love to see more information about low flow showers. I bought 2 low flow shower heads and they are dreadful, I had an excelent low flow rose but the holes in the brass plate the water sprays from erode eventually and the manufacturer stopped making that model shower rose, fools. I looked into the "low flow" roses I recently bought and they are just high flow roses with a restrictor in the top. I removed the restrictor as I like a good shower but I know there are better roses out there. I want a good low flow rose if I can find one.

[hobbit]

Is anyone actually producing drain-water heat recovery system
parts available to mere mortals? This sounds like it could be
a relatively huge factor if properly designed.
.
_H*

[drees]

I've got this detachable low-flow "waterpik ecoflow" shower head which I picked up from my local home depot which is by far the best low-flow shower head I've ever used. I suppose I should measure the actual flow rate, but it claims to be 1.5 gpm.

[jayman]

Originally Posted by hobbit

Is anyone actually producing drain-water heat recovery system
parts available to mere mortals? This sounds like it could be
a relatively huge factor if properly designed.
.
_H*

Commercially, yes. Especially for combined-cycle heat/power installations. Don't know of any for homeowner use

[fuzzy1]

Originally Posted by hobbit

Is anyone actually producing drain-water heat recovery system
parts available to mere mortals? This sounds like it could be
a relatively huge factor if properly designed.

Someone has displayed a heat exchanger, a copper drain pipe with a spiral wrap of incoming water line, at the local annual Home Show. I first saw in quite a few years ago, but don't currently have information.

Originally Posted by drees

I've got this detachable low-flow "waterpik ecoflow" shower head which I picked up from my local home depot which is by far the best low-flow shower head I've ever used. I suppose I should measure the actual flow rate, but it claims to be 1.5 gpm.

My current Waterpik head (replacing a quarter-century-old model) is similar to this, from Costco. When the dial is turned to use only the center ring of nozzles, I am satisfied with the flow when turned down to 0.6-0.7 gpm. DW always uses full blast to penetrate her hair, but my chrome dome is much easier to wash.

I absolutely detest those common shower valves that have only one flow rate, full blast. I greatly prefer a lower flow, to allow a more leisurely shower without feeling guilty about wasting water and heat.

[Shawn Clark]

Originally Posted by hobbit

Is anyone actually producing drain-water heat recovery system
parts available to mere mortals? This sounds like it could be
a relatively huge factor if properly designed.

I've roughed out some numbers for my MBR shower and it is signficant, perhaps 20% of our total water heating demand if I could do countercurrent with 5 F approach. The area I estimated to do the job is fairly large though...enough to discourage me from taking if any further at this stage because of material costs.

Getting significant heat transfer contact area from a spiral wrap of a drain line is pretty difficult (many engineers have found this out from heat wrapping lines trying to make a poor man's heat exchanger), and this is a challenging service: low velocities, little driving head on the shower drain side, fouling on the shower drain side.

I see some major drawbacks for small users: 1. We've already minimized the water flow so the payback is slim. 2. There is going to be a lot of thermal lag and losses due to the heat sink effect of the drain line and tubing. 3. Low flows mean lower drain temp. at the same given shower temp.--I measured 106 F shower temp, 96 F at the drain and estimated the best I could hope for was about 91 F feed to the water heater in a countercurrent arrangement.

The one design I've seen is for a falling film drain surface with a wrapped coil. I've done coil wraps like this myself with process lines and they aren't exactly stellar performers. If I were to do this I would make my own.

[Shawn Clark]

Originally Posted by drees

I've got this detachable low-flow "waterpik ecoflow" shower head which I picked up from my local home depot which is by far the best low-flow shower head I've ever used. I suppose I should measure the actual flow rate, but it claims to be 1.5 gpm.

I hadn't seen that one. I'll take a look at it the next time I'm in Home Depot. All the ones I've seen have been 2.5 gpm heads. The wall mount 3 mode 1.5 gpm would be worth experimenting with.

I detest the handheld types though. I had them (don't remember the manufacturer) in a rental in Houston and they were nothing but trouble. I don't want to hold the silly thing and the holder never seems to keep the head positioned properly so I would fiddle with it multiple times every time I showered and still be dissatisfied every time. The spray was poor and I ended up boring them out to get more flow. Then the kids decided to use the hose as a handhold when they had their first showers...that led to some breakage and replacement.

[Shawn Clark]

Originally Posted by patsparks

I'd love to see more information about low flow showers. I bought 2 low flow shower heads and they are dreadful, I had an excelent low flow rose but the holes in the brass plate the water sprays from erode eventually and the manufacturer stopped making that model shower rose, fools. I looked into the "low flow" roses I recently bought and they are just high flow roses with a restrictor in the top. I removed the restrictor as I like a good shower but I know there are better roses out there. I want a good low flow rose if I can find one.

I'm using two High Sierra's and a Roadrunner at the moment and am happy with them. I'll try to post update information about this in new thread later this week. I discovered some problems which were resolved.

[drees]

Originally Posted by Shawn Clark

I hadn't seen that one. I'll take a look at it the next time I'm in Home Depot. All the ones I've seen have been 2.5 gpm heads. The wall mount 3 mode 1.5 gpm would be worth experimenting with.

I detest the handheld types though. I had them (don't remember the manufacturer) in a rental in Houston and they were nothing but trouble. I don't want to hold the silly thing and the holder never seems to keep the head positioned properly so I would fiddle with it multiple times every time I showered and still be dissatisfied every time. The spray was poor and I ended up boring them out to get more flow. Then the kids decided to use the hose as a handhold when they had their first showers...that led to some breakage and replacement.

Well, with this particular one, I haven't had any of the problems you've mentioned after a year of use. The only problem with the head moving is because my wife moves it so I have to move it back. Kids haven't managed to break it yet, either.

I actually find with the really low flow heads being able to move it is beneficial since then you are able to directly water exactly where you need it.