Water heater
I have a 2 bath house with 2 adults and 1 child plus 1 on the way. First bath has a 17″ deep 5′ tub and the master has a walk in shower with dual shower heads. The shower heads are Moen rain style and they dump the water which we like. Downfall is we run out of hot water quickly especially if the wife and I are taking a shower at the same time. With both heads running we are out of hot water in 10-12 mins. We have a 50 gallon AO Smith electric currently. We have natural gas available. We have a very small mechanical room about 3×7 that houses WH, furnace, water softener and IT equipment. Do we upgrade to a gas 80 gallon or do we go for the high cost of a tankless? I own a construction business and have an account at a plumbing supply store and can install myself.
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You should have plenty of hot water with that 50. Check that both elements are working not just one. Turning up the temp makes a big difference. Add a mixing valve to cool the flow down to a safer level if you want. This will also give you more hot water.
I thought about the elements also. Had my electrician out and he checked and both elements are good and have power. I did a flow test on my shower head and they are dumping about 4.5/gpm.
Is that 4.5 gpm per head, or with both combined?
4.5 per head
That's a ridiculous amount of total flow, and it would take a MASSIVE tankless (or a gia-normous tank) to keep up.
Lower flow shower heads would be a good start.
A tankless is going to limit your max flow, since the flow rate is burner-limited.
For major gusher-showers a drainwater heat recovery heat exchanger can make a significant difference in "apparent capacity" by pre-heating the cold water feed to both the water heater and the cold side of the shower mixers with the heat that is otherwise literally going down the drain. To have a significant impact (~50% heat recovery or better) it would need to replace at least a 4-5' length of vertical drain down stream of the shower. At high flow there is a pressure drop (but not as severe as the pressure drop on a tankless water heater), but they're not all the same. The current best in class is EcoDrain's VT1000 series, in terms of both pressure drop and heat recovery efficiency:
https://ecodrain.com/en/products/
https://www.greenbuildingadvisor.com/green-basics/drain-water-heat-recovery
The biggest one that fits if the "best" choice, since the marginal increase in size is more than paid off in higher return efficiency.
It won't do anything for tub fills, but for showers it's like adding major sized burner or heater element, but a burner/element that doesn't increase the energy bill.
Do you know if ecodrain’s horizontal model work well? I’m interested in using this method to extend our hot water heater but we are building a ranch on a conditioned crawl and there isn’t enough vertical space for the VT1000.
Thanks
Alan
The house is a ranch on a slab, so that wouldn't be an option. I am doing a remodel on a ranch with a basement and have a nice long horizontal area I could install one that is very close to the water heater. I will have to do more research on these. Thanks
Dana,
Are those EcoDrain VT1000 units available to buy? I see on their web site that they sell to "major commercial projects" but nothing about retail sales.
Call or email them. In the past they have been willing to sell direct to retail customers in the US (at retail type prices), since (SFAIK) they don't have US distributors.
Renewability sells their PowerPipe series heat recovery units direct too, despite using the big orange box store as a US distributor.
You could use a tankless gas water heater in series with, and ahead of, your existing tank-type water heater. In this way the tank will provide the high flow rate you need, the tankless will act as a preheater and help make the hot water last longer even if it can’t manage the entire flow on its own.
Downsides are you’ll still have the standby energy use of the tank-type water heater even though you have a tankless water heater.
You could use a tempering (mixing) valve to let you run really hot water in the tank but still keep the hot water temperature supplied to your house at safe levels. Note that these are thermostatic valves, not regular three-way mixing valves.
Drain water heat recovery systems can help too. I’m no so sure a horizontal unit will be as effective as a vertical unit since the vertical unit would likely have more interface area since water in vertical drains tends to go down the circumference of the pipe as a sheet. With a horizontal drain, the water flows like a little river in the bottom part of the pipe only. I’d imaging a horizontal heat exchanger would allow for this, but I don’t think it would be able to be as efficient as a vertical unit. I have no experience with the horizontal units to be able to know for sure.
Bill
Try finding a lower flow shower head you find acceptable. I don’t know the rain style, but in traditional spray style, there are a lot of good options in the 2-2.5gpm range.
The good ones incorporate more air into the stream to make it feel like more water.
Im with Matt on this. Seems like the greener option.
Search through the Grohe site, there are a number of rain heads that are 2.5 gpm.
The common way I've seen is the dual tankless heaters. You might have to upgrade your service, these use a lot of BTU.
An in between might be a larger commercial electric water heater. Some come with 10kw elements. The larger volume combined with running it hotter should get you enough for a longer shower.
Is putting a small tankless heater close to a distant bathroom a common strategy to deal with a long distance from the main hot water heater? Not as a primary source of hot water for that bathroom, but just to heat water on demand and run the hot water from the main tank through that tankless unit... I assume as the hot water comes through the tankless, the water just runs through the unit...
Sorry for the highjack...
Thanks,
Alan
The small tankless water heaters used that way are very low flow, so good for handwashing but not so much for a shower. Better options to deal with getting hot water to a distant fixture are to insulate your hot water lines (which also has other benefits), or putting in a recirculating loop. Recirculating loops can be setup to only run when needed, or on timers, so they don’t necessarily have to run continuously.
I use a thermosyphon type of recirculating loop in my own home. It has the advantage of not needing a circulation pump (so no electricity use and no pump to break), but the downside is more gas use since the constantly running loop adds more thermal losses to the tank in standby service. If you go this route, BE SURE to insulate ALL of the pipe in the recirculating loop!
Bill
9gpm for a shower is a lot. Your 12min shower with that setup is equivalent to a 45min shower with a typical head. That's the biggest contributor to your problem.
As already suggested, get a lower flow shower head. Your problems will be solved. 4.5 GPM is ridiculous, Mine are less than 2.0 and there's plenty of water.
At a 60F incoming to shower head temperature difference (45F at the street or well, 105F at the shower) 9 gpm is a heat rate of about 270,000 BTU/hr, which completely outstrips the biggest residential tankless water heaters.
At a combined 2 gpm + 2 gpm = 4 gpm that becomes a still substantial 120,000 BTU/hr, but a 199,000 BTU/hr-in tankless can still cover that with some amount of margin.
An 80 gallon heat pump water heater would extend the showering time to something like 15-18 minutes and still use less electricity than the current 50 gallon electric solution. That's the direction to be steering if there is no place for a drainwater heat recovery unit- bigger storage capacity, not bigger burner capacity.
I was thinking Heat Pump but would I have to worry about the size on my utility room? 3x7 room located inside of a bathroom. So you walk into a 6x7 bathroom and then there are sliding doors into the utility room.
There are ducted heat pump water heaters to deal with the small room problem. (Rheems are pre-configured with connection sheet metal for ducting with round ducts.)
It may be easier to install the water heater in the utility room and run pipes instead of ducts.
I called Ecodrain today.
Their horizontal drain water heat recovery pipe is not available.
Does anyone know of an alternative?
Thanks!
I looked into a heat recovery drain a little while ago and couldn't find one that is still being manufactured. They seem to come and go.
Seems like it wouldn't be that hard to make one.
New shower heads are cheap, compared with alternatives. Get a couple and try them. We have a two person shower with Moen heads. Not Sure how many gpm, but we never run out of hot water from our 50 gallon tank.
Not a green solution, but natural gas would help. A lot more BTU's available in gas vs electric. A 50 gallon electric is simply not compatible with a high flow luxury shower.
I have a dual rain shower configuration that is even worse than yours. It uses 6gpm per head, 12gpm total and full bore; and that is measured by me with a 5 gallon bucket and a stop watch. I rarely run it full bore, but my wife does. I installed two 200kBTUh takeless gas heaters to run it without concern of running a tank dry even while other people are using hot water. They are the 90% efficient models. If I shut one off, both showerheads will still run good enough, but at less than 12gpm. The tankless models regulate the outgoing water supply to maintain temperature so the end result is you get less water flow and pressure rather than a cold shower.
The point is I think you can get by with a single 200k BTUH natural gas tankless heater and run both shower heads with endless hot water.
>Not a green solution, but natural gas would help. A lot more BTU's available in gas vs electric.
Do the math: 9 gpm at 60 F temperature rise is a heat rate of about 270,000 BTU/hr. Swapping out a 50 gallon electric for a 50 gallon fossil-burner with 35K or even 75K burner buys at most a FEW SECONDs of additional showering time. It's not about the fuel, it's about the heat rate.
>"I installed two 200kBTUh takeless gas heaters to run it without concern of running a tank dry even while other people are using hot water. They are the 90% efficient models. If I shut one off, both showerheads will still run good enough, but at less than 12gpm. The tankless models regulate the outgoing water supply to maintain temperature so the end result is you get less water flow and pressure rather than a cold shower."
I guess that would save the cost of flow restrictors at the showerheads, eh? :-)
Most 199K tankless units have a pretty serious pressure drop at higher flow rates. It's on the order of 10 psi @ 4 gpm, and twice that at 6 gpm. A pressure drop that big on the hot side of the mixer that big often interacts with the anti-scald features of shower mixers. So while a single big-burner gas tankless MIGHT work here, it's not guaranteed. A bigger tank is a more assured solution.
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Well first off, I thought showering with a friend saved water....First thing to consider is your utility room size. Is there room to add a second WH and is your flue or chimney sufficiently sized to add a gas WH? My thoughts would be to add a 40 gal gas WH in series with your electric, that way there you have a larger volume of stored HW and better regulation of temperature with the gas heater. I would keep the electric until it dies and then replace that with a second gas heater giving you more control whereby you can lower the first tank in the summer and raise it in the winter as necessary, sometimes just the pilot alone will keep the water warm enough depending on how long it sits between use. Once the second tank reaches temp it should stay off as it is fed with hot water from the first tank so ultimately you are really only using one tank to heat the water you need. and you'll have the volume of HW you need.
As far as the shower heads, I find that just using the volume control on the shower valve is sufficient by itself to give you a longer, hotter shower since it reduces the amount of cold water that goes into the mix. If you can do it yourself, installing separate H and C controls can do this for you too.
Shaun, I have shower heads that integrate air injection with the water to make it feel like more volume. I'm in California so I think they're limited to 2 gpm.
At full flow it feels like a river dumping on me. I usually run the shower at about half that flow, if not less.
You might check out that solution before replacing your water heater.
I think a spam post has reactivated this old threat (not that Tom and Mike haven't offered some useful information).