Need solution for more hot water

The house we recently purchased has a 1 year old gas hot water heater that appears to be undersized for the house.

The house has 5-6 bedrooms and we are a family of 6, yet the tank is only 50 gallons. We typically run out of hot water after 1-2 baths and a couple of showers.

Seems to me we have a couple of choices:

  1. Take fewer, shorter, and more spaced out baths and showers (not acceptable per my wife and kids :)

  1. Replace with new larger tank (100 gallons?) (however, existing unit is almost new, so this sounds a bit wasteful)

  2. Get a second hot water heater (Can this be done? Can you just get another storage tank or do you need 2 separate full heaters? Are they connected in series or parallel?)

  1. Get some type of booster such as an auxilliary tankless heater? (Is there some type of booster that only comes on when the main tank is depleted and that would not be too costly to purchase or install?)

Assuming that #1 is not an option (at least per my wife), what approach would you recommend?

Reply to
blueman
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Without knowing your specifics, option #2 is probably your least cost and most efficient (and space saving) option. Make sure that it is also gas and check the recovery times before you purchase.

Come to think of it, the showers should not place much of a load on a gas hot water heater. Are you using low-flow shower heads? These are limited to 2.5 gallons per minute. Showers generally use less hot water than baths so if you are going to change your lifestyle and tell the family to take more showers - less baths, that would be one thing to try.

Drain the sediment from your existing hot water heater with the valve provided. You might get a marginal improvement in the recovey time.

Option # 3 - Second heaters are sometimes installed in series with an existing tank (if local codes permit). However, most of the time you will then have two large tanks of standing hot water and the losses (through the tank and the pipes at the top) that are characteristic with this configuration. If you go this route, you might want to make the first retrofit tank in the loop electric and put a timer on it so that it only operates during your (presumably morning) peak demand times. Gas heaters are cheaper and more efficient, but it is virtually impossible to put a timer on a standard gas heater with a standing pilot.

Option #4 - Having a tankless heater will be expensive in terms of capital cost for the BTU's and flow rate that you require for your peak hot water demand. If you can configure one bathroom to use the tankless heater and you have room for it and the required exhaust, then perhaps it would work for you. (electric tankless is not recommended unless you live in someplace like Washington State next to a hydroelectric dam and your electricity is dirt cheap).

If it were me, and none of the cheap solutions were viable, I would go with option #2 as the least cost option.

Beachcomber

Reply to
Beachcomber

Recover time and Btu input are what is critical, you dont need

100gallon just a proper 50 for your load. It is possible it is not set up right the gas line may be to small or something else not giving full gas flow if it is in fact a properly sized heater. Flow restrictors on sinks and showers and a good tech would be a starting point.
Reply to
m Ransley

I agree, but I would add one additional possibility. While not likely on a one year old heater, it is possible the dip tube is defective and that will greatly reduce capacity.

That 50 gal tank should be able to handle your needs unless there is a mechanic problem of some kind.

Reply to
Joseph Meehan

Joseph,

I disagree with both you and Mr. Ransely. He has a family of 6 and 50 gallons of hot water in the morning. He'll run out of hot water by the fourth shower. By the sixth shower the water will be very cold. He can adjust the thermostat to make the water hotter but this can be very dangerous or he can find more hot water. I think he needs a bigger water heater. A 6 bedroom house should have a water heater which will supply enough water for 10 people in my opinion.

Dave M.

Reply to
David Martel

Use a lower flow shower head or turn the know up on the hot water heater. f you haven't already insulated all exposed hot water pipes, do that first. When I insulated my hot water pipes (just the exposed ones in the basement) it was the equivalent of turning up the hot water heater a notch.

Reply to
scott_z500

Or add a greywater heat exchanger...

10 SCREEN 9:KEY OFF:PI=4*ATN(1) 20 DOP=.752'pipe od (inches) 30 DIP=.622'pipe id (inches) 40 NTURNS=34.5/DOP'number of turns in layer 50 RLOOP=23.5/2'loop radius (inches) 60 CLOOP=2*PI*RLOOP/12'loop od (feet) 70 LLAYER=NTURNS*CLOOP'length per layer (feet) 80 L=LLAYER 90 PRINT 1,RLOOP/DOP,NTURNS,LLAYER 100 RLOOP=RLOOP-DOP'loop radius (inches) 110 CLOOP=2*PI*RLOOP/12'loop od (feet) 120 LLAYER=NTURNS*CLOOP'length per layer (feet) 130 L=L+LLAYER 140 PRINT 2,RLOOP/DOP,NTURNS,LLAYER 150 RLOOP=RLOOP-DOP'loop radius (inches) 160 CLOOP=2*PI*RLOOP/12'loop od (feet) 170 LLAYER=NTURNS*CLOOP'length per layer (feet) 180 L=L+LLAYER 190 PRINT 3,RLOOP/DOP,NTURNS,LLAYER 200 AP=AP+L*PI*(DOP+DIP)/2/12'pipe area (ft^2) 210 VP=VP+L*PI*(DIP/2/12)^2*7.48'pipe volume (gallons) 220 FLOW=1.25'gpm 230 LL=L/3'average layer pipe length (feet) 240 FL=FLOW/3'average flow per layer (gpm) 250 PL=.0004227*LL*FL^1.852*DIP^-4.871'Hazen-Williams pressure loss (psi) 260 PRINT L,AP,VP,PL 270 C=60*FLOW*8.33'burst heat capacity rate (Btu/h-F) 280 NTU=30*AP/C'burst NTU for counterflow heat exchanger 290 E=NTU/(NTU+1)'burst heat exchanger efficacy 300 TCI=55'fresh water inlet temp (F) 310 TSH=110'shower head outlet temp (F) 320 THI=105'greywater inlet (shower drain) temp (F) 330 THO=TCI+E*(THI-TCI)'burst fresh water outlet temp (F) 340 ESAVINGS=100*(1-(TSH-THO)/(TSH-TCI))'burst % savings 350 VHW=120'daily hot water consumption (gallons) 360 CKWH=.1'$/kWh 370 DSAVINGS=365*ESAVINGS/100*VHW*8.33*(TSH-TCI)/3412*CKWH'$/year savings 380 PRINT NTU,E,THO,ESAVINGS,DSAVINGS 390 C=VHW*8.33/24'continuous heat capacity rate (Btu/h-F) 400 NTU=30*AP/C'continuous NTU for counterflow heat exchanger 410 E=NTU/(NTU+1)'continuous heat exchanger efficacy 420 THO=TCI+E*(THI-TCI)'continuous fresh water outlet temp (F) 430 ESAVINGS=100*(1-(TSH-THO)/(TSH-TCI))'continuous % savings 440 DSAVINGS=365*ESAVINGS/100*VHW*8.33*(TSH-TCI)/3412*CKWH'$/year savings 450 PRINT NTU,E,THO,ESAVINGS,DSAVINGS 1 15.625 45.87767 282.2525 2 14.625 45.87767 264.1884 3 13.625 45.87767 246.1242 792.5651 142.5478 12.50964 .2229677 6.84503 .8725308 98.62654 79.32098 466.5099 102.6754 .9903546 104.5177 90.03223 529.5059

Nick

Reply to
nicksanspam

What about turning up the water heater temperature and then installing a tempering valve on the hot water outlet to reduce the temperature? Is this a reasonable idea?

Cheers, Wayne

Reply to
Wayne Whitney

The tanklless setup is a good option. Depending on the use patterns, you may want to convert the most used bathroom to that style and leave the 50 gallon tank for the rest. There was a thread here yesterday about that type of heater and it pointed to a web page for more information.

Why store and heat more water that will sit there all day?

Reply to
Edwin Pawlowski

Dave you have never seen what an apt building uses I take it. I have 35 tennants on a 90 gallon 235000 btu AO Smith , always plenty of hot water, even with 15 showers running at the same time. Heating 100 gallons is not as efficient as a good H. O. 50 for a home. As I sad it is all about Btu and Temp rise. Not your HD cheapie of course. But not knowing what he has it just may not be working right ex. gas line to small

Reply to
m Ransley

I assume that you have raised the setting on the heater to the hottest setting. Install flow restricters on the showers that the children use.

When I was married with 3 kids we had a 30 gallon heater. The kids got 5 minutes in the shower and 10 if they took a bath. I put the heater on max just before the first shower.

Better check to see that your gas line will handle the additional load. More storage is a poor answer in my opninion

This will be complicated and can not be answered except by inspection.

You do not mention where the water heater is. If it is outside, insulate it. especially the top with at least R-6. That will slow down the losses. Insulate the hot water line at the heater and anywhere else you can easily get at it.

Reply to
SQLit

If you realy find your unit will not handle it and it operates correctly look into a Rinnai tankless, you cant run out of hot water and will save in its operation as it is more efficient than regular water heaters. But first try what everyone has mentioned. Shower restrictors and showering first before running a tub, and put a time limit on showering, hot water can easily use 30% of your gas usage even if you live in a cold climate.

Reply to
m Ransley

I believe the label says that it has a recovery rate of 36 gallon/hour and that the burner is 70K BTU. Is this considered a "good" recovery rate or is it undersized for the load I describe above?

Reply to
blueman

Ransley,

I don't believe that this is an apartment building, it is a house with 6 bedrooms. The water heater is undersized for the morning use. Let's look at your claim for the apartment. You have 90 gals. of hot water (125 degrees?). With 15 showers running and low flow restrictors in place you'll probably draw 30 gals of water out of the heater in each minute. Your water heater will be out of hot water in 3 minutes (a very short shower) unless you can put a lot of heat into that unit very quickly. You can post about Btu and temp rise but I don't find you credible.

Dave M.

Reply to
David Martel

Well Dave you ought to see what apartment buildings use . Go prove it to your self or prove me wrong . 200000 btu+ and a 2"-3" water inlet systems are normal for 14 unit buildings. I cant say when people shower , but there is never a hot water complaint. These are not HD heaters but 1500-3000$ units . high output.

Reply to
m Ransley

I'm not sure the apt style WH is the correct solution for OP homeowner.

That said Ransley numbers seem credible to me, the unit he describes can deliver about 4 gpm of water from 55F to 125F.

It's like the best of both worlds; 90gal storage & 4 gpm

I've got a house with a 75 gal WH (about 75,000btu/hr I think ) serves

3 full baths & you definitely don't want to be the 4th or 5th shower (esp if those early ones were"longish")

It also serves a 75 gallon spa tub that it cannot fill with premixed water; you've got to start out with all hot & as themp falls it just turns out right.

It's all about the BTU's per minute demanded & the available supply; you've got to store, be able to generate it or reduce instaneous demand.

Existing gas line will determine what capacity is available.

I've toyed with OP's Option #4 but the cost of tankless has detered me. My idea would be set the temperature of the tank heater above the temperature of the tankless. The tankless would come on only when needed.

This kinda defeats the purpose of the tankless but the problem with tankless is when current demand exceeds capacity you no longer get "hot water" you get "warmed water".

Most tankless can only supply 2 major users at the same;

two showers shower & bath shower & washer etc

as soon as you add the 3rd user on the tankless, performance will suffer

Maybe tank + tankless makes sense; I've haven't been sure enough (or cold showered enough) to do anything about

The Takagi T-KJr. Tankless Water Heater is a lower capacity (140,000 btu/hr max) & lower priced unit that might make sense.

cheers Bob

Reply to
BobK207

This is Turtle.

Some Quick Recovery runs about 1 ga. per minute.

TURTLE

Reply to
TURTLE

Taking the numbers a bit further, the recovery rate (by my calculations) would only give you about 7.2 gallons/minute or enough for about 3.5 showers steady state after the first 3 minutes depleted the existing tank.

I did: (235000 BTU/hour)/(60 minutes/hour)/(8.33 lb/gallon of water)/(65 degree temp difference between 45degree source and desired 100 degree shower) = 7.23 gallons/minute

This is an optimistic case, assuming 100% efficiency and no issues of mixing new cold water in at a faster pace than heat can be applied.

Reply to
blueman

I agree with David on this. We have a 40 gallon gas water heater and it is barely good for two showers, But then we have a high flow shower head too. Even before with a water saving shower head it was not unusual to run out on a long shower. my daughter will drain the heater all by herself with her 1/2 hour showers! Water shaving shower heads would be a must with 6 showers every morning, plus a higher capacity heater. And shorten the time in the shower! Greg

Reply to
Greg O

Pretty typical heater. Most 50 gallon heaters will only recover as much as a

40 gallon. You need what my boss has! He has a Buderus boiler with a add on heat exchanger for domestic hot water. The recovery rate on his is 258 gallons per hour! He says he NEVER runs out of hot water.
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better have some cash stashed away! Greg
Reply to
Greg O

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