Need solution for more hot water

Page 1 of 2  
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 :)
2. Replace with new larger tank (100 gallons?) (however, existing unit is almost new, so this sounds a bit wasteful)
3. 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?)
4. 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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
m Ransley wrote:

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.
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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 NTURNS4.5/DOP'number of turns in layer 50 RLOOP#.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`*FLOW*8.33'burst heat capacity rate (Btu/h-F) 280 NTU0*AP/C'burst NTU for counterflow heat exchanger 290 E=NTU/(NTU+1)'burst heat exchanger efficacy 300 TCIU'fresh water inlet temp (F) 310 TSH0'shower head outlet temp (F) 320 THI5'greywater inlet (shower drain) temp (F) 330 THO=TCI+E*(THI-TCI)'burst fresh water outlet temp (F) 340 ESAVINGS0*(1-(TSH-THO)/(TSH-TCI))'burst % savings 350 VHW0'daily hot water consumption (gallons) 360 CKWH=.1'$/kWh 370 DSAVINGS65*ESAVINGS/100*VHW*8.33*(TSH-TCI)/3412*CKWH'$/year savings 380 PRINT NTU,E,THO,ESAVINGS,DSAVINGS 390 C=VHW*8.33/24'continuous heat capacity rate (Btu/h-F) 400 NTU0*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 ESAVINGS0*(1-(TSH-THO)/(TSH-TCI))'continuous % savings 440 DSAVINGS65*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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob,
Unfortunately Ransley's numbers were 200000+ Btu. This isn't helpful since a Btu is the amount of energy needed to raise 1 lb. of water 1 deg. F. If he had reported Btu/hr. his number might be helpful. Let's go on the assumption that he meant Btu/hr. Lets also assume that the water enters the water heater at 50 deg. and is heated to 125 deg.. I think a gal of water is around 8 lbs. so the system is capable of heating about 330 gals of water in an hour from cold to hot. Not bad but it can't keep up with the consumption of 30 gals of hot water/min. in his shower example since it is producing 5 gals of hot water/min. (I'm rounding a lot of numbers here). Ransley means to be helpful but frequently doesn't recognize when he is misguided. His example doesn't seem to work and his example has nothing to do with the OP's problem.
Dave M.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Dave- I agree, he was sloppy with his units but since he said it cost ~$1500 to 3000, was fed with a 2" water line & was meant for an apt. I figured it 200,000+ BTU per hour.
I based my calcs on that & factored in the efficiency.
IMO your assumption of 15 instanteous showers is a bit unrealistic.
Based on average shower length & the temporal distribution of shower start times you could develop a more reasonable estimate of the sustained short term hot water demand. I agree that a 5 bedroom / 6 person household needs either; a hot water warden or more hot water generation / capacity.
I've got a 4 (sometimes 5) bedroom / 3 full bath house on a 75 gallon LP WH; when there's lots of showering going on I make sure I'm not last. :)
We all kind of got off topic...............what is the best solution(s) for the OP?
Does anyone have a comment of the tankless fed by a medium sized tank WH; use the tankless as a "peaking unit"
or does it make sense to feed the tank with the tankless but change the control method so the tankless only helps when "needed"??
I have not thought this out completely but my gut tells that just get a bigger (or more) tank style WH's is not the best approach. Also the tankless units are big $'s and they only support 2 instantanous uses; as soon as three showers are running you're in trouble.
I guess demand reduction (shorter showers, low flow heads & shower spacing) is needed unless capital equipment & energy usage $'s are no concern.
cheers Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I guess you guys havnt been in many apt buildings of 12-14 units 200000 - 235000 Btu 100 gallon tanks are the norm and do the job fine, even heating cold midwest water in winter. I dont know the recovery rate , and these are 2" incomming high recovery heaters costing 3-4 times as much as a HD 100 gallon. I truely dought full loads from all aptartments are ever reached. I was just pointing out that 100 gallon tanks can be overkill for a house and higher output smaller tanks should be looked at first , just as one person said that he should put in a 100 gallon, there are options to look at. There are tankless by Rinnai that will handle his needs. There are tankless that are being refitted into apt buildings, sometimes 2-4 are ganged together. I beleive Rinnai has units up to near 280000 btu. With some restriction the 180000 btu Rinnai will handle 3 showers. There again it depends on incomming water temp. I go from a low of 35f to 72f incomming. At 70 f my small 117000 bosch could easily handle 2 showers that are restricted, I know ive tried it. All I need for a shower is 102f with no cold added. I know this may not help the OP , I first tried to point out conservation and the possibility his unit simply may be under fed gas or not operating right. I have also seen bad thermostats that dont cut in till temp has dropped very low 15-20f , hurting immediate recovery for constant use. He could possibly use a secondary tankless but for a bit more Rinnai has a model that will work for all his needs .
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I am doing a 4 plex with 2 beds in each unit. I use a single Super Store indirect 40 gallon tank. The boiler running the building has domestic priority and has an output of around 230 k btus. It works. If someone starts running out they shorten their shower time. If I were doing it again I would probably go to a 50 gallon tank. This is in Northeast and I have heard no complaints this winter.
Oreo

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote in message

This is Turtle.
http://www.foreverhotwater.com/ Name Rinnal tanklessheater.
It is gas and can run 3 showers at one time and all hot water from 90F to 140F water temp. 24 hours a day / 7 days a week and never run out. Flow rate will be a little over 9 gal. per minute which the average shower will take 3 gal. per minute or less. On average they burn 30% less natural gas than a tank type. The burner heat rate can be from 15K btu to 200k btu , which also comes in Propane also , which all is controlled by a digital thermostat that you can set the water temp. as you like it from 70F to 160F . Also comes with 10 year warranty.
Bad part , it will cost you over $1K for heater and materials -- No labor. I have seen one work and they work fine and all the hot water you want.
TURTLE
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@webtv.net (m Ransley) writes:

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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.