Flutterby™! : hot water on demand 2008-01-22 21:02:28.757084+00

hot water on demand

2008-01-22 21:02:28.757084+00 by Dan Lyke 14 comments

This weekend while off looking at various cabinet styles so we'd have a basis for discussion (still trying to figure out how I'm going to cut elliptical profiles on the door faces...), we ran across the Metlund D'Mand hot water pump. It's a pump and a thermostat, put it across the hot and cold lines in the furthest fixture from the hot water heater, press a button, it pumps hot into cold 'til it detects hot water. $350 (8GPM, 10 feet of head) and up.

My dad pointed out the Watts Premier pump that uses a pump at the water heater and a mechanical valve at the furthest fixture, $255 (3.4GPM, 3.5 feet of head, but I'm not sure I can compare 'em across the board that way). Anyone used these toys and have an opinion? I suppose a start would be to fill a bucket at the bathtub, measure how much water it takes to get hot water, and compare based on that...

Interesting. I have been considering one of these. I'm not sure they make financial sense except where there are water shortages.

So further info gleaned from reading the Lang AutoCirc docs (which I don't have a good link to, here's an HVACQuick product page for the Lang AutoCirc) says that more than 4GPM in 1/2" copper pipe or 8GPM in 3/4" copper pipe can cause excessive erosion and early deterioration.

Water-savings wise I don't think it makes a cost justifiable difference, and I'm sure it costs more for heating if this is an always on system, so some way to say "turn this on only for the next few minutes" is important to me.

Where I see the value is in convenience. A button next to the bed that says "prime the shower" so that it's already warm when I stumble from the bedroom to the bathroom in the morning, or even one in the bathroom that says "I'm going to wash my hands once I'm done with the toilet" has value to me.

As it hit me this weekend, we were comparing the price of something like this to replacing our television with something high def and flat screen, and dollars per hour of enjoyment it seemed like cutting out those few minutes in the cold house of waiting for the shower water to warm up every morning would end up winning out over the occasional rented DVD.

A further note: The lack of adjustment on the temperature also seems like it needs a modern temperature controlled shower valve. Which means we need to wait on that 'til we re-do the shower controls.

#Comment Re: New Home Owner made: 2008-01-23 04:28:43.816829+00 by: Bob Batchelder

A bit off the subject, but perhaps a contribution to you Dan. My wife and I live in Dunlap, TN (I understand you get down this way from time to time), and we built our dream/retirement home on 25 acres of red oak forest (we bought for 3k/acre in 1998). There are two things we did that made a big contribution to the quality of our home that I recommend to you. We had the electricians install a whole house surge protector (you need to spend about $250 for a decent quality), we had the plumbers install a tank-less hot water heater (we got an Aqua-Star, which I think has been bought by Bosch). We have never runout of hot water, and we only pay for hot water that we use.

I've thought about more dramatic surge protection, but out here in California thunderstorms and the attendant power issues are far less prevalent than y'all run into in Tennessee (I can count the number of thunderstorms I've been aware of in the 12+ years I've been out here on one hand), and the state of power supplies is pretty amazing nowadays. In fact, now that I'm back in an area that doesn't have much in the way of power outages and am running mostly on laptops anyway I'm considering giving up my Clary UPS.

On the tankless hot water heater, I'm very interested in learning more, especially since the right form factor might make the water pump gadget moot!

If you can get a gas-line or 220V to the bathroom, tankless hot-water there solves most of the complaints. But after 4 years in my house, I'm still trying to figure out the logistics of doing that. The water's there, obviously, but I still can't figure a way to get a gas-line up there without tearing apart a wall downstairs, most likely in the kitchen. Sigh. Every project seems like a new variation on sokoban...

I think this is going to be the summer of tearing apart the bathroom. The tile in the shower-surround is starting to pop from the wall because I didn't re-grout it when I moved in, and Something Must Be Done. Might as well re-do the whole thing while I'm at it, right?

I looked at the systems that pump from the hot into the cold. My house was built in 1929, and the opinion of the experts is that such a system would be likely to make me very unhappy when one of the old galvanized pipes decided to give out some morning when I was preparing for a shower.

In our place the gas line is easy, just run it in the crawl space. The feed from the meter to the hot water and heater already run under there. I'd need some tools, but nothing incredibly impossible to get.

I'm thinking that when we get to tearing up the bathroom we should seriously consider re-running copper rather than the galvanized we've got right now. I think it'll probably be easier to sweat a whole new set of runs than to unscrew some of those connections. Probably be trivial to run PEX, but I don't trust plastics.

You're probably going to want to use bottled or filtered water to make your coffee with once you've added this sort of gizmo... It probably wouldn't be unhealthy, but it'd be like making coffee w/ water from the hot tap.

We run a filter for drinking water anyway. Growing up on a good well spoiled me for city water, even when it's good city water.

If you know how to use a torch, which you do, it's trivial to run copper. Just expensive compared to PEX. You can actually trust plastic these days as long as you understand how to properly install the fittings. That's not difficult.

#Comment Re: made: 2008-01-23 18:47:26.638742+00 by: Dan Lyke [edit history]

Yeah, Larry, I've always had more problem getting the Teflon taped screw fittings at the valves watertight than sweated copper joints. Looks like 3/4" nominal is about $5/foot for type M and $6.75 for type L.

I still need to be convinced on PEX, especially as I'm running across various notes about using the hot water recirculators and making sure that plastic piping is safe for constant use, not just intermittent use. Hmmm... looks like PEX rated for continuous recirculation is about a tenth the price of copper. Gulp. Must plant the seeds early so that Charlene feels okay with it...

Well, I'm trying to find something more recent than 2005, but it seems like the rules on PEX in California are in flux, whether for legitimate health reasons or for political reasons, the pipefitter's union doesn't like it. Copper may be more expensive, but I think it's unlikely to be controversial, and for a few hundred bucks seems worth the risk mitigation.

Of course the pipefitters are going to be against it. It installs in half the time or less.

#Comment Re: made: 2008-01-24 11:37:21.822066+00 by: meuon [edit history]

Like Dan, I can sweat copper and like how durable it is. I've done some bad plumbing, but when I've done it right, in copper, it's art. :)

Nancy and I have the same issue with showers at the house, and I think my real answer will soon be an on demand heater near the bathroom, and another smaller one near the kitchen. Mostly because the gas hot water heater is old, and we don't use a lot of hot water. Nancy already washes clothes in cold water. I think it'll save money and energy long term, and stop the 2 minutes of running water to get hot water to the bathroom. For some odd reasons, on-demand heaters are more expensive than I think they should be...