Running out of hot water in shower

lee_7

if they are new, they should be there unless removed by installer

anp

Running out of hot water in showers

Hi all,

We just moved into a 1968 yr built house in the North east.
It has an oil fired furnace, which supplies the hot water to the bathrooms etc as well as circulates the hot water for the baseboard heat.
In the past we have always lived in houses with electric heat and water heater, so this is all new.
We have three heating zones and as far as we know, the house stays pretty warm.
As far as the faucets in the bathrooms, kitchen, dishwasher etc. there is a good supply of hot water.
However, the hot water runs out in the showers within the first five minutes. We have had 3 plumbers look at the problem so far and none of them are able to resolve the problem.
We put in a new mixing valve at the boiler, this made it a little better than before when we were getting hot water only for a couple of minutes.
What is puzzling is that it is happening only at the showers. It is also happening at all the 3 showers in the 3 bathrooms.
The 3 plumbers each had a different solution for the problem (each on just as expensive):
1. Boil the coil to remove any deposits/scaling.
2. Connect a 50 gal Electric water heater.
3. Connect a hot water booster to boost the heat.

My questions for each solution are:
1. How come there is scalding hot water in the faucets? Does that not indicate that the coil is fine? Moreover, if I touch the piping at the boiler, it is very hot.Why only the showers?
2. What will happen if I do connect an electric water heater? Will it start up everytime I am turning on the room heat too? If that is the case, I would be incurring a huge electricity bill for something that is working fine (baseboard heat).
3. For the hot water booster too, if it is based on electricity, I am asking for a big bill every month.

My question is why is this happening ony at the showers?
One plumber suggested it may be due to the single valve at the shower that adjusts the hot/cold. But in another bathroom in the house, I have two seperate valves for the hot and cold water and I still run out of hot water in there within 5 minutes.

If anyone has any experience with this kind of problem, please help because its bearable now but will not be during the cold days of winter!!

Thanks in advance.

kevin coppinger_4

the classic tankless.

What you are explaining is classic problem w/ flow and heat transfer. The coil has most likely scaled up w/calcium. This slows the transfer of heat to the coil and w/ the flow of water throug the tankless coil it cannot keep up. You get the initial heat flow at the faucet because you have water sitting in the coil for longer periods of time and the flow is less. An indirect water heater would be an answer...but seeing that your boiler is nearly 40 years old a new boiler would also be in the cards. energy is not cheap...
A less expensive answer would be to either replace the coil or flush it w/ acid to clean out the scale in the coil...

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anp

Does the coil also heat the water for the baseboard heat?

Thanks, Kevin.
>> An indirect water heater would be an answer...


So, if I go for this option, will the new water heater also kick in when the water is heating to supply the baseboard heat? That means I will be using up oil as well as electricity for heating up the whole house.
In other words, does the coil also heat the water for the baseboard heat? If it does, then, the house will also not heat up for lack of hot water in the baseboard heating?

Dave Yates (GrandPAH)_1

long term savings & safety

An indirect water heater is the best investment to make. Over a 30-year period of time, it's life cycle costs will be half as expensive as a conventional gas water heater and even better when compared to an electric water heater.

Costs more up front though, but if you can look past the initial installation costs, it's a much better option.

Your mix vlv is either installed incorrectly, defective, or not a certified ASSE 1016/1017 device. That's where your scalding hot water issue is centered. An indirect will resolve that quite nicely, although I'd still recommend you have a certified ASSE 1016/1017 scald-guard valve installed to regulate outlet temps.

You'll also be in a position to alter your existing boiler to a 'heat-on-demand-only' operation, which will save fuel. Doesn't make sense to let a poorly insulated "hot box" stand idle while cycling to maintain its internal temperature as it does now to ensure you'll have a rapid hot water response. And, if you keep this boiler, you can add outdoor reset to further conserve fuel.

Or, if your budget will allow, go for the full monte & upgrade the boiler too.

heatboy

With 3 Showers in 3 Bathrooms.......

..... you would be hard pressed to keep up with a large indirect, let alone just a tankless coil, if more than one shower was operating. Without seeing and touching your system troubleshooting these kinds of issues is impossible. The Northeast is pretty big. Where exactly?

hb

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Tom Hopkins

I urge you to dismiss the three plumbers!

None has it right, although each is "close."

You have multiple options, none cheap, but none all that expenive.

First, let's clarify the problem:
1. Most tankless coils are capable of producing close to 1 gallon per minute of hot water at the shower head - per 40,000 BTU's of boiler/burner firing rate.

2. A "water saver" shower head delivers 3 GPM of hot water, therefore, the boiler/burner must fire 120,000 BTU's to "keep up." If you have two showers going at once, you need double the boiler/burner - as well as a tankless coil that can utilize all those BTU's - a 6 GPM coil (way larger than typically installed in all but a mansion-like setup).

3. If your home has "standard" shower heads, they use ~ 5 GPM, exceeding the capability of the boiler/burner AND coil's capacity - within a minute or two!

4. With a "tankless coil," if not fitted with a mixing valve, the water initially can be at scalding, 3rd degree burn temps - definitely a dangerous situation when kids and guests (who are unaware of this danger) use the hot water.

5. Mixing valves do NOT add hot water output, they merely make it safer, possibly adding a few minutes to a 3 minute supply.

6. Unless the boiler is getting under 80% efficiency, an indirect domestc hot water storage tank/device is the answer. If the boiler is a dog, simply adding a gas water heater is the cheapest way out. If the boiler is NOT a dog (under 80% efficient) the solution is not any of the options offered so far.

THE LIKELY SOLUTION:

Use the tankless coil as a "source" to heat an indirect domestic hot water storage tank, either a 40 or 60-gallon (with a coil/boiler of 100,000 BTU input, or more) and it will work like this:

The shower will take potable water from the IST (indirect storage tank) that is stored and already hot. If the aquastat (a water, not air-sensing thermostat you set to whatever it takes to get all the hot water you need) will tell the boiler the IST is running low on water temps, and to "turn on" to replentish the waning water temp situation. Because the IST has 40-60 gallons of already warm water inside, you cannot "suddenly" run out. The tankless coil stores perhaps a gallon of water - making it vulnerable to "run-out" as you already know all too well.

Interestingly, in the winter, you might NEVER RUN OUT! This is because the boiler will be firing for heat anyhow. Almost all boilers have a "thingy" that "says," If someone's in the shower, I am not allowed to heat the house for those few minutes, since the bather trumps the heat. The thingy makes the boiler heat bath water, preventing heat - until the boiler gets back to the "thingy's" set point.

It is insane to run a boiler 24/7 all summer - heating the basement and having the A/C on, trying to cool the very heat coming through the floors to the living area. By putting a timer on the IST, we can prevent the boiler from firing to replentish the IST when it isn't needed, in most cases, that will be between 10 p.m. and 6 a.m.

If everyone in the house is out at school or work, the timer can also turn off the boiler from 8 a.m. til 4 p.m.

The potential savings with this timer device are very large!

The cost of fuel being what it is, we have our boiler active for only an hour in the a.m. and an hour in the evening. And, with 40-gallons of insulated storage in the IST, it keeps way more than enough hot water for the spans between the "on" times you allow the boiler to fire.

There are many options available; but none of those were in your recommend plumber's venue.

You might want to use the "Find a Professional" link at the top left of this web page. Plug in your zip code and take a look.

Your issues are NOT plumbing per se. A sad generaliztion: Most plumbers are NOT the best heating guys; further, most heating guys are NOT the best plumbers. Any exceptions to that generalization will be listed in the Find a Professional link above.

Hope this helps.

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Dave Yates (GrandPAH)_1

three - can do!

HB,

Our morning schedule sees three showers running at the same time. When we relied solely on the indirect, we rarely ran out of hot water - unless Mike got about a ten-minute head start(G). Now that we've got 120-gallons of liquid sunshine upstream of the 75-gallon indirect, it seldom runs unless we've had a few days of cloudy weather.

140K modcon feeding the indirect on an as-needed basis.

34-year life cycle cost for electric tank-style is in excess of 40K (includes two replacements). Tankless electric runs a close second and only lags by about 1K (includes one replacement at 20th year). Indirect coupled to a modcon hi-e is mid-20K (includes one replacement at 20th year) & does not include the boiler - just the indirect, fuel costs, EF rating and electricity for the circ. Calculations included a 5% per year uptick for all costs. I'd need to re-run my numbers for oil with a standard boiler (I've got life cycle numbers for oil-fired water heaters).

Bob Gagnon plumbing and heating

Free Quick Fix

An indirect or storage tank is the best answer for the long term, but for the short term you can simply slow the water down at the shower valve so it goes slower through the tankless coil, allowing it to pick up more heat from the boiler, like the bath faucets. I got by for years using this method, then I finally put in the tank. Bob Gagnon

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steveb_3

.

In keeping with the notion that slowing the flow of water through the showers could make the hot showers last longer, have you checked to see that you have low flow shower heads? Just changing to low flow heads from high flow heads will make the hot water last much longer. You will also use much less water with low flow heads.

Charles_8

My coil won't even do one shower

I have this exact same problem (oil fired steam system with tankless coil), although with only one shower, and a few questions came to mind:

1) Is it possible to clean the coil both on the inside (through the lines) and the outside (within the boiler) without removing it from the boiler? (Those 20 year old rusty bolts look like they're just waiting to break off). If so, is there a cleaning solution I can put in the boiler water? I don't think the oil company tech does anything at the annual service except burner nozzle and fuel filter changes, CO & draft readings.


2) The discussion of indirect storage tanks interests me. How do you get the water to circulate back through the coil? Doesn't that require a pump?

3) Could I simply feed the output from the coil into an electric 40 gallon water heater, thereby using a "mix" of oil and electricity? Would I still need the mixing valve?

4) In the summer I would then like to shut the boiler down, and make hot water via the electric heater only. I've seen discussions here about condensation and rust forming on the boiler if it's shut down though?

thanks for any tips.
-Charles

Tom Hopkins

Chas.

Unless you have hard water, the tankless coil is NOT scaled up. Unless the flow is restricted, you probably can be sure liming is NOT the problem.

Yes. A small inexpensive circulator IS required to do an indirect.

Unless you live someplace where electricty is under 10-cents/KW, electric is prohibitively expensive - compared to gas or oil.

As mentioned in the nearby post, a timer is key to huge energy savings. Few need to bath at 3 a.m. A cheap timer will pay for itself in a week!

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Bob Gagnon plumbing and heating

Right Steve

Plus I bet the shower valve has a temp limit that mixes cold water with the hot, to protect you from that inital blast of real hot water, unfortunately mixes in cold water when you really don't want to. Bob Gagnon

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Charles_8

Timers? Some basic physics questions.

I have city water and it's fairly hard. The house had very rusty iron pipes for years, which have recently been replaced with PVC and copper. No flow restrictor though. I do think that my thermostatic mixing valve is stuck since there seems to be no temperature regulation whatsoever other than the aquastat. I guess I can run a bottle brush into the lines when I've got the system open to see how cruddy they may be (on the inside). So there should not be deposits on the outside of the coil either?

Regarding timers - shutting it off at night will indeed prevent energy from being consumed during periods of inactivity. In the idle state, energy is consumed to maintain the heat differential (between the water at 160F and the basement at 60F). But the next morning it will have to run longer to heat all the water in the tank back up to 160F.

So: say X BTUs are wasted to maintain the temperature in 24 hrs, but Y BTUs are consumed during the 2 hr of actual use. If it takes 120,000 BTU/h while generating hot water, that's at least 240k BTU for Y in one day, plus the energy required to reheat the tank. How many BTUs are wasted while idling? I don't know. 5,000/hr? That'd be 120k BTU for the day, so getting that down would definitely be worth it. Or is it closer to only 1,000/hr? Or 20,000?


I don't know which term predominates. I know it will make SOME difference, but how great will the actual savings really be? Do you have some actual example numbers?

thanks
-Charles

anp

Running one shower at a time.

thanks, guys. A lot of this stuff is very technical and I may ask some dumb questions further along. Some clarification I need to add, I am not running all 3 showers at the same time. Just one at a time. And all display the same characteristic of running out of hot water in a few minutes. I will try the easy options today- change one shower head to the 2.5 g one and not turn the hot water valve all the way (at the shower), but leave it midway and see if it lasts longer.

lee_7

most tankless coils are 5 gpm, which yes have to be installed in a boiler sized properly for them. A tankless coil WILL NOT provide enough hot water to heat an indirect tank alone. It can preheat water entering an electric heater or gas/oil heater. If the flow of hot water out of the shower with seperate hot and cold handles does not diminish but the hot water does, the OUTSIDE of the coil is probably clogged. Where in the northeast are you located? Putting the indirect tank in would be great if money is not an option, but here outside Philly the money tree has lost it leaves. The least expensive option is to pull coil and clean inside and out. If that doesn't work, it should only cost $300- $400 to find out, over the $2000 - $3000 for indirect tank. Just my opinion.

lee_7

Where are you located? I'm outside Philly and would be glad to come look for you if you are in the area.

Dave Yates (GrandPAH)_1

could be from

CT & involved with fuel cells?

Charles_8

Preheating with tankless...

I've got a thread going over on plbg.com on this same subject, and after "thinking out loud" I realized that there's another problem.

Does this make sense: preheated water from the coil will only flow into the big electric tank when hot water is flowing out of it through a shower or faucet. Most of the time (22 hrs out of 24, at least in my house) the tank is sitting there idling and its heat loss has to be made up by the electric element.

Would it be possible to add a circulator pump to the electric weater heater, resulting in a combination of tankless preheat to the electric/storage tank? In other words, the system would be an indirect heater with electric supplementation. I drew a diagram and it looks like two check valves would be required at the input to the coil (one from the street supply, one from the circulator).

-Charles

lee_7

yea it is possible with so repiping. System 2000 has a great diagram in their service tech book for making an electric water heater into indirect tank. With a little ingenuity anything is possible.

GREG LAUER

check something

THE GUY HAS HOT WATER AT THE FAUCETS. has anyone checked to see if the watersaver is still in the shower head?

mtfallsmikey

Don't dismiss us plumbers just yet!

I've run into this many times even with standard gas/electric hot water heaters. High incoming water pressure, no PRV, no showerhead flow restrictors can cause "no hot water" after a brief period of time running the shower/tub.

anp

Shower water savers, PRVs, flow restrictors??

Clearly you all are dealing with somebody too big of a novice (me). :-) But I have no idea what water savers or flow restrictors are. When I went to Home depot, they told me that all shower heads come equipped with 2.5g restrictors and you dont need to install anything extra.
Some more explanation would be greatly appreciated.

Bob Gagnon plumbing and heating

PRV'S and flow restrictors

Just slow the water down. Can you do that with your shower valve with the water turned all the way to hot? Bob Gagnon

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anp

In two of the bathrooms, we have a single control - push/pull to start or stop flow, turn it to the left for hot and to the right for cold. For the third bathroom, there are two seperate controls, one for hot and one for cold. I have tried keeping the hot open half way, but the hot water is discontinuous, runs out, starts coming again and runs out again.

Bob Gagnon plumbing and heating

you could

restrict it at the shower head, with a lever type shutoff. You can get them in chrome for shower heads. Bob Gagnon

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anp

trying to eliminate shower head as the problem

I tried to understand the problem by elimination process and ran the water from the faucet in the tub, without lifting the lever on it (which I would otherwise use to make the water go to the shower head). The problem still exists, so I guess the shower head gets eliminated from the picture?

anp

trying to eliminate shower head as the problem

I tried to understand the problem by elimination process and ran the water from the faucet in the tub, without lifting the lever on it (which I would otherwise use to make the water go to the shower head). The problem still exists, so I guess the shower head gets eliminated from the picture?

brucewo1b

sorry but no

The worse faucet to use to check a problem is the tub as it runs faster than most other faucets in the house and it will be the worse when it come to lack of hot water at the coil, now try running that tub faucet at about quarter flow and see what happens then take a one gallon measuring device and see how long it takes to fill and come back with those numbers.

Bob Gagnon plumbing and heating

The shower head isn't the problem

water flowing too quickly is the problem, it will flow full blast through the spout, there is no way to slow it down. Bob Gagnon

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lee_7

where are you located? Sounds like you need someone in person to look at issue.

Larry C_9

Checking the shower head flow rate

To check the flow rate of the shower is simple. Take a plastic bucket of a moderate size (1 to 3 gallons) Hold the empty bucket up to the shower nozzle, turn on the shower, and time how long it takes to fill up the bucket. The volume of the bucket (gallons) divided by the number of minutes it took to fill it up, equals the flow rate. Newer showers should be around 2.5 gallons per minute.