Water heater decisions


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Old 02-01-16, 06:38 AM
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Water heater decisions

In the process of building a new house and trying to decide on the best strategy for hot water heating.

We tried to be efficient with our floor plan design, and were able to clump the bathrooms and laundry room in one corner of the 2nd floor of our house. The guest bath is downstairs, almost directly underneath the baths upstairs. The only outlier is the kitchen and a half bath, which is on the other side of the house.

The house is all electric, and there are a couple of things I'm concerned about...

First
The traditional placement of a hot water heater is in the basement (if you have one), but I am concerned about the long run from the heater to the 2nd floor. I am also concerned about the long run to the kitchen and half bath.

One solution to this would be to locate the heater in the upstairs laundry room, which would mean that the hot water run would only be a few feet to all the fixtures upstairs, and just a one-story run to the guest bath below. The concern here would obviously be having a water tank on the 2nd floor, and the risk of water damage if something leaks. However, there is already some risk involved with this in the laundry room already, and I wonder if I can include some waterproofing features into this room to help lessen the damage if something happened. This doesn't solve the problem of having a long run to the kitchen, but I wonder if that should be solved by a separate heater just for those fixtures, placed directly under the kitchen.

Second
I am concerned about recovery times for electric water heaters. We have a family of four, and pretty soon we are going to have 4 showers going in a short period of time. We have always had gas heaters, which have a quicker recovery time, and the kids are younger now so they normally bathe at night, but in a few years they are going to be showering in the morning like everyone else.

A possible solution to this would be a tankless heater. In addition to the efficiency, the advantages of a tankless heater would be that I could place it in the upstairs laundry without worry of a tank leaking and causing damage. However, I worry about it being able to keep up with the demand. I would imagine there will be times when two showers are running at the same time, and I'd worry that the heater couldn't keep up with demand. I know that an electric tankless heater is a different animal than a gas tankless, in terms of output. I have done some reading on GBA and other sites and it looks like the jury is still out on these devices, or at least they were a few years ago when those articles were written. I've also wondered if adding a small tank between the heater and the fixtures would be a fix to some of the drawbacks to tankless (the "cold water sandwich" and problems with low flow not triggering the heater), but then you are also adding the back the drawbacks of tank-type heaters. Plus, you'd have the expense of both installations.

And then a third thought I had was a heat pump water heater in the basement. This would not solve any of the problems above, but I would like to have wide plank hardwood flooring but have been warned about cupping due to the moisture from the basement. This is a little off topic, but I wonder if the HPWH would do enough de-humidifying in the basement to help in this regard. Or, would a couple of dehumidifiers be better? Or, would neither of those do enough to prevent the cupping?

Sorry this post is so long, but there is a lot to consider.
 
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Old 02-01-16, 06:56 AM
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A couple of observations:

You could certainly have a waterproofed mud floor with a floor drain in the second floor laundry. Much like a very large shower base. This is a good idea in a 2nd floor laundry in any case and would alleviate your concern about installing the water heater there.

The time to address dampness concerns in the basement is during construction. Insulating under the slab, good vapor barrier under the slab, waterproofing membrane on the foundation, drainage mat on the foundation, good foundation drains, and proper backfill will ensure your basement is dry and moisture free. This is an area often shortchanged by builders as it is unseen after backfill and usually doesn't cause trouble for many years. But I think you are better off spending an extra few grand to get the best foundation waterproofing you can while it's easy and relatively cheap to do.
You can easily spend a few grand running a dehumidifier for years...why not eliminate the need from the start.

Having said that, I still don't believe solid wood flooring would be a good choice in a basement, but there are plenty of engineered floors that can be used below grade in a dry basement.
 
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Old 02-01-16, 06:56 AM
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How about 2 water heaters, one of each or both tankless, with a by pass valve? If one breaks, the other can be used?
 
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Old 02-01-16, 09:25 AM
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Depending on your water quality.... a tankless electric heater may not be the most trouble free way to go. Also.... the current demand is extremely high with tankless heaters which means you may be required to increase the size of your service to run them.
 
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Old 02-01-16, 09:31 AM
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Sorry for not being clear. The hardwood will go on the first floor, directly above the basement.

I think we have done a good job with the basement construction. Put down a vapor barrier under foundation, waterproof membrane on outside, plus some sort of fiberboard (maybe your waterproof mat?), plus foundation drains and gravel back fill.
 
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Old 02-02-16, 07:14 AM
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An electric tankless MIGHT be acceptable for the kitchen where the flow rate is fairly small and almost always to only one fixture at a time; either the sink faucet or the dishwasher. I would never advocate an electric tankless for any situation where the flow could be as low as maybe a half-gallon per minute (washing hands) to maybe seven GPM such as two showers running simultaneously. High flow rates require HUGE electric heaters and quite honestly, they don't stage all that well. Gas-fired tankless would be a completely different story but since you have already decided it is to be an "all-electric" house that option is out the door.

Further, even in an all-electric home it is rarely necessary to have more than a 200 ampere service, an electric tankless capable of providing seven GPM may require an upgrade to 320 ampere service and THAT will be a significant cost increase that would probably take a couple of decades of tankless savings to amortize IF it would ever cost out.

And, as PJ mentioned, if you have high mineral content in your water the tankless is anything but maintenance free and this is especially true of electric tankless.

Nor, in my opinion, is the heat pump water heater a viable option. The heat pump ONLY operates with a slight drop of temperature whereas the resistance elements will "take over" for any significant draw of hot water. The heat pump functions when a small amount of water, say for hand washing, is used OR for normal standby losses. My OPINION is that the increased cost AND probable maintenance of the heat pump water heater will likely be higher over the useful life of the unit than would be the operating cost of a traditional electric heater with an extra insulation blanket.
 
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Old 02-02-16, 11:53 AM
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And my 2 cent....

Install two 40 gal electrics. Pipe both in parallel . This allows you to use one heater until the kids get bigger. Alternate the heaters every 6 months of so.. Or just run both..

For your other concerns install a recirc pump with a timer so you have hot water to the farthust areas of the home instantly..

More info when you post back...
 
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Old 02-02-16, 01:05 PM
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Thanks for the responses. It sounds like votes against tankless water heaters are a unanimous, at least for large volumes of hot water. I still wonder if a tankless heater would work for the far side of the house that will only have a kitchen sink, dishwasher, and lavatory sink. If a tankless would work in that situation, I like the idea of that over a recirc. pump, which I'm worried about being an energy drain as you lose hot water radiating out of the pipes.

I like the idea of keeping the heater as close to point of use as possible, and you are right Carbide Tipped, I had planned on implementing some waterproofing in the laundry room to guard against leaks from the washer, so adding the heater may not be a big deal anyway, other than increasing the risk of something actually happening (2 devices have to be riskier than 1, right?).

lawrosa - I hadn't thought about the idea of 2 heaters in parallel. That is an interesting thought. I like the idea of shutting one down during low use times...not only now while they are young but in the future when they are grown and out of the house. The only problem with that idea is that I'm not sure I have enough room in the laundry room for 2 heaters. The room is just 7x9.5, which is enough room physically, but that would cut into storage and hanging space. I have plenty of room in the basement for 2 heaters, but that means the runs are longer up to the 2nd floor bathrooms. I don't know, maybe there is enough room in the laundry room for 2 heaters. I'll have to study on that.
 
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Old 02-02-16, 01:16 PM
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I would put them in the basement IMO..

that will only have a kitchen sink, dishwasher, and lavatory sink.
Put a small 20 gallon over there then, but I would just run a pump with the timer...off the 2 40 gal

They retro fit. all you need is check valve or valse at the farthest runs.. Maybe one near kitchen in that lave, and one in 2nd floor lave..
Often if other baths are on same branch the one check covers the whole area.

Instant Hot Water Recirculating System with Built-In Timer - Watts


I would forget about tankless..
 
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Old 02-02-16, 01:54 PM
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Gas-fired tankless is often an excellent choice for prolonged flows of hot water. One example is hot water to showers in a gymnasium. To use a tank-type heater you would have to have one with a capacity of a minimum of five hundred gallons and it would take several hours (depending on electric element size) to recover.

Mike and I are going to disagree here but I NEVER advocate installing less than an eighty gallon electric water heater. It takes no more electricity to heat the water drawn from an eighty gallon tank than it does if the draw is from a 40 gallon tank. Also, the standby losses are so low on electric heaters as to not even be considered. Back some 15 years ago, in my previous house, I went through a three-day electrical outage and still had enough hot water in my eighty gallon tank to take a reasonably quick shower on the third day. You could not do that with a forty gallon tank. An electric tankless will, of course, produce NO hot water during a power outage.

Other factors are whether or not you like long, hot showers (I do) and if you can train everyone in the house to take "navy" showers. A navy shower is to get wet, turn off the water completely, soap up, turn the water on, rinse, turn the water off and get out of the shower. If you can do this then a shower lasts about 3 minutes. Myself, I like to have that hot water beating my back and I rarely spend anything less than 15-20 minutes (often more) under the shower. I don't like low-flow shower heads either.
 
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Old 02-02-16, 02:57 PM
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Mike and I are going to disagree here but I NEVER advocate installing less than an eighty gallon electric water heater. It takes no more electricity to heat the water drawn from an eighty gallon tank than it does if the draw is from a 40 gallon tank.

With the new codes I believe all units of this size are heat pump models... And they come with a 2000 $$$ price tag....


FHPT-80 - AO Smith FHPT-80 - 80 Gallon Voltex Residential Hybrid Electric Heat Pump Water Heater (6 Year Warranty)

Where two 40s your a bit cheaper at about 1200... and no heat pump...

http://www.supplyhouse.com/AO-Smith-...ter-Tall-Model

But ahhh for same price get 2 50.s IMO...

ENT-50 - AO Smith ENT-50 - 50 Gallon ProMax Residential Electric Water Heater - Tall Model
 
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Old 02-02-16, 04:18 PM
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Thanks, Mike. I was hoping that stupid federal regulation concerning heat pumps on larger electric water heaters had been repealed.
 
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Old 02-03-16, 05:45 AM
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Again, thanks for the replies.

Mike - What is the reasoning for preferring the basement location for the heater(s)? Is it space? Water leakage? Ease of installation?

I have seen where some people suggest a drain water heat recovery system like "power pipe", where the incoming cold water is wrapped around the drain pipe out of the showers so the warm outgoing water can help warm up the incoming cold water. Any thoughts on this as a possible solution or help?
 
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Old 02-03-16, 09:58 AM
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I have seen where some people suggest a drain water heat recovery system like "power pipe", where the incoming cold water is wrapped around the drain pipe out of the showers so the warm outgoing water can help warm up the incoming cold water.
Only works on vertical metal drains and the drains pretty much have to be confined to just shower drains. The longer the drain the better it works. Unfortunately, running two stories of 2-inch copper DWV piping with 1/2-inch soft copper wrapped around it will be rather expensive, most likely with a payback of at least ten years and maybe no true payback at all. They DO make these heat exchangers in shorter sizes but the shorter they are the less effective they are.
 
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Old 02-03-16, 11:19 AM
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Mike - What is the reasoning for preferring the basement location for the heater(s)? Is it space? Water leakage? Ease of installation?

All of the above.. IMO a basement is where the stuff should be.. ( If you ever had/saw a leaking heater from a second floor you can only wish they were in the basement. ) Lots of damage..

Unless you can get them in a pan of some sort that drains outside...




I have seen where some people suggest a drain water heat recovery system like "power pipe", where the incoming cold water is wrapped around the drain pipe out of the showers so the warm outgoing water can help warm up the incoming cold water. Any thoughts on this as a possible solution or help?
LOL ... why would you want that? Dont feed into the hype of those.. It would be a waste of time and money...

If you think hot water down the drain will heat the copper, dont you think the opposite would be true also? ( That the cold water will cool the waste pipe before it even gets hot?)
 
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Old 02-03-16, 12:03 PM
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Haha, that wouldn't be the sole source of the hot water. It would only help to increase the incoming cold water so that the heater doesn't have to work as hard to get the water hot. Cold water cooling the waste pipe just returns it to normal cold water going into the hot water heater.
 
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Old 02-03-16, 12:13 PM
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Unless you can get them in a pan of some sort that drains outside...
The potential location of the upstairs heater would be in the upstairs laundry room, which would have some waterproofing already to minimize damage from leaks.
 
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Old 02-03-16, 12:31 PM
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which would have some waterproofing already to minimize damage from leaks.
What exactly would that be?
 
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Old 02-03-16, 01:07 PM
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A waterproof floor and a central drain. If I was really paranoid I guess I could put some sort of waterproofing on the walls near the heater and washer to protect it from spraying water.
 
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Old 02-03-16, 01:37 PM
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A waterproof floor and a central drain.
A drain would help but I don't know of any floor that is truly waterproof.
 
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Old 02-03-16, 04:33 PM
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You could make a wooden floor waterproof by using fiberglass techniques. It would be expensive and labor intensive to build but it could be done. Had I been in better health and had more time I would have done it at my sister's house in the upstairs laundry room. As it was, I put in a floor drain (actually into the plastic washing machine tray) and replaced better than half of the subfloor with real plywood rather than the OSB (or whatever it was) that had swollen from the water from either the WM leak or the toilet on the other side of the wall upchucking.
 
 

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