Hot water supply

Getting reports of upstairs shower at our rental hogging all the hot water when someone is also showering in the downstairs bathroom. Kind of surprised me, since the water heater is downstairs.

Any idea what to look for?

TIA,

IP

Do you have an electric water heater?

Is the problem really showering at the same time or do you mean somebody showed about 6:30am and when somebody else showers at 6:45am they run out of hot water?

If yes to both, I am going to nominate the lower heating element on your water heater. And if the water heater was installed 5 years or more ago, I say replace the water heater. (More than a few people do not agree with my water heater replacement ideas. But plumbers are not cheap and the labor part of replacing an element is not trivial.)

Two water heaters, one for each rental unit. On different meters. End of issue, happier renters.

Rob
Rule Breaker Home Fool
He is no fool who gives what he cannot keep to gain what he cannot lose.

2 Likes

IMO they should just take turns showering. Jeez. And really, the upstairs shower gets no hot water, or just not as much as desired?

But, if you want to solve it, first step would be to have the water pressure into the house checked. If it’s low, that would be a big job to fix.

If that’s OK, you might need wider diameter pipes to the upstairs shower, and a thermostatic or pressure-balanced shower valve, which is a good idea in all baths and showers anyway to reduce the risk of scalding.

Also, a 75 gallon water heater would be good, so tenants can run laundry, dishwasher, showers at once or sequentially without running out of hot water. Alternatively, “instant hot water” is popular, although my current house has that, and the hot water temperature is not uniform. So, I’d need a thermostatic valve; a pressure-balancing one wouldn’t provide uniform temperature given that the incoming water on the hot side isn’t uniform in the first place. So, DH & I just set our showers at “very warm” instead of “as hot as we can stand it,” to allow for some temperature variation.

It never occurred to us that this was something the landlord should fix. Aren’t your tenants leaving soon? Maybe for next tenants, you could specify that the hot water is “as is.”
Or, sell the house. :slight_smile:

Do you have an electric water heater?

Is the problem really showering at the same time or do you mean somebody showed about 6:30am and when somebody else showers at 6:45am they run out of hot water?

Yes to electric. It’s a at the same time issue with the upstairs shower stealing all the hot water if someone steps in to shower when the downstairs one is in operations.

If yes to both, I am going to nominate the lower heating element on your water heater. And if the water heater was installed 5 years or more ago, I say replace the water heater. (More than a few people do not agree with my water heater replacement ideas. But plumbers are not cheap and the labor part of replacing an element is not trivial.)

Water heater is probably over 10 years old. We have owned for 5 and frankly never done maintenance on it. Was thinking about trying to drain potential sediment out of it? But if it’s the heater itself, why don’t both showers go cold? The upstairs never has a problem with getting the hot water, it just takes all of it if needed.

IP,
needing a primer on how to do the sediment drainage thing

Two water heaters, one for each rental unit. On different meters. End of issue, happier renters.

Single family home with 4 professional women. Don’t get me started on clogged drains!

IP,
who has taught these young ladies a considerable amount about maintaining a house

It never occurred to us that this was something the landlord should fix. Aren’t your tenants leaving soon? Maybe for next tenants, you could specify that the hot water is “as is.”
Or, sell the house. :slight_smile:

LOL. Selling the house is tempting, but it is a nice diversification from the stock market. I keep on waffling between selling and renting when their lease is up in May.

I am actually going to miss these 4 young ladies as they go off to greener pastures. I just wished they had mentioned this problem earlier, as I had a plumber at the house both Thursday and Friday, doing upgrades, and I could have had him look at it then.

We like to market our property as a must have property and get premium rent. I’ve always thought that endless hot water, (though for a price,) is my birthright as an American. Cold showers should not be necessary.

Thanks for all of your ideas. It is the upstairs shower that gets all the hot water when in competition with the downstairs. I found that particularly weird given the water heater is close to the downstairs shower.

IP

1 Like

Water heater is probably over 10 years old. We have owned for 5 and frankly never done maintenance on it. Was thinking about trying to drain potential sediment out of it? But if it’s the heater itself, why don’t both showers go cold? The upstairs never has a problem with getting the hot water, it just takes all of it if needed.

But given there is no problem getting hot water upstairs, only downstairs, is this a problem with the heater or the supply route?

IP

needing a primer on how to do the sediment drainage thing

  1. Connect hose to lower spigot on water heater. Put the other end out the door, and somewhere a mineral buildup won’t kill your favorite plant. You will end up with a bunch of salts there. Run it into a strainer or your flour sifter if need be. The volume will be less than a baseball, likely.

  2. Inform the tenants that the water will be off for the next 2 hours. Tell them they may not use the washing machine, dishwasher, or anything else that automatically calls for water. (These things have resistance heaters for water which can burn out if they’re cycled but there’s no water.)

  3. SHUT OFF THE BREAKER TO THE HEATER !!!

  4. Shut off the water main.

  5. Open the water heater spigot. Don’t open it too far, they often need only a half turn, and opening too far may cause it to fall off in your hand. Judge after you see how much is coming out the hose.

  6. Open another faucet somewhere “upstairs” in the house so air can enter the pipes and let the water out.

  7. Wait for it to drain.

  8. Shut off the “upstairs air” faucet you opened.

  9. Turn on the water main to continue flushing out the tank.

  10. When you stop seeing crud come out, you are done.


  1. Close the lower spigot on the water heater.

  2. Open another spigot somewhere “upstairs” to relieve pressure.

  3. Wait for the water heater to fill. You will know this when the stream of water from the “upstairs” spigot becomes reliably full stream. There will be lots of sputtering; ignore it.

  4. Switch the breaker back on.

  5. Purge the upstairs lines by opening each and every faucet and flush every toilet. (Some of those will sound explosive. It’s just the air going through.)

Done.


If the problem continues, I’d vote for the lower heating element. Actually I’d vote for that first; removing the sediment (especially from an electric) won’t matter that much for “volume”, it will just increase the cost of the actual heating.

Replacing a lower element is not costly, but at 10 years you’re close to replacing the whole thing anyway. Consider a heat-pump WH if you’re going to own for more than 4-5 years; they’re more expensive but vastly more efficient. Your water heater is probably 15-20% of total electric bill, a heat pump heater will knock that down to 5%, maybe less.

Buy your replacement at a home center store and have one of their contractors install it, it’s cheaper than buying from a plumbing outfit. However I know some people refuse to use HD or Lowe’s contractors, but I’ve not had trouble ever.

A 40 gallon tank should be sufficient for 2 adults, if you’re running multiple tenants and/or children etc. size appropriately. An “apartment” WH is 25 gallons and people make do, but more is better (also more expensive to heat.)

I have watched a good plumber replace a lower element without even draining the tank. He unscrews the old one, slaps his hand over the hole and jams in the new one and screws it in. A bit messy but really pretty fast. It’s a 20 minute job.

It could be the heating element is fine and it’s the thermostat that’s not passing the message to heat after the top element reaches temperature. You can just do a resistance check with a multimeter on the two contacts of the element. If there’s resistance it’s good. If not, it’s broken. They just “snap” like a carrot after enough cycles. Replacing a thermostat is not hard but takes longer. It could be the upper or lower, a plumber will figure it out.

I use the word “upstairs” faucet but it doesn’t have to be “upstairs”, it just has to be upstream of the water heater. It could even be a basement sink, it’s just a path for air to go backwards and replace the water in the lines and heater.

Wait a few hours after this post to see if anyone chimes in with something I’ve forgotten. It certainly happens. In fact I’m going to go back and number the steps to make corrections easier.

5 Likes

Thank you so much, Goofy. Very appreciated.

IP

I left out a step.

12A: Turn the master water back on. If it’s a 90-degree ball valve open it slowly over a few seconds to avoid a quick on-rush of pressure to toilets or pipe joints.

1 Like

Think long and hard about getting any electric water heater under 80 gallons in a rental unit that can have 4 or more adults.

Draining a water heater sounds easy and preferable to buying a new one. Right up to the point the valve fails to close properly. Usually these failures are not in the flowing area, but in the damn drip drip drip area. There is a reason the instructions say drain every 6 months – it has more to do with being able to close the valve than sediment building up.

Heatpump water heaters can be a good deal. When they first came out they had painfully slow recovery rates. Recovery rate is how many gallons of water can be heated from cold water to hot water per hour. For tank type water heaters, gas is the fastest - residential pumps up to 40 gallons per hour (90F degree rise). Electrics about 20F. (Commercial units are much higher - but required different gas/electric connections.)

Insist on speaking to a satisfied customer before buying heat pump water heater from anybody. The largest plumbing/HVAC company locally had some many upset heat pump water heater customers 5 years ago, they stopped selling them. I noticed within the last few years Rheem’s heat pump water heaters systems have had a fundamental redesign. They now are designed and marketed as Hybrid water heaters with recover rates approaching electric water heaters.

In case you don’t know how an electric water heater operates, these have two heating elements. One about 10 inches from the top and another about 10 inches from the bottom. The electrical setup is such that only one element will heat at a time. The factory (and proper) settings are the top element should be set a few degrees lower temp than the bottom element. So normally the lower element heats the whole tank to say 120F. In use hot water come off the top and cold water enters is piped internally to the bottom of the tank. A normal shower might use 1 gallon per minute of hot water.

One or two people showering at the same time for 10 minutes shower will not notice any difference in water temp coming out of a normal sized water heater because the cold water is at the bottom of the tank.

Now if the bottom element is burned out, only the upper 8 or 10 inches of water is hot. The rest is room temperature or colder. In an 80 gallon tank the upper element might be 10 or 12 gallons. So with just one person showering, after one 10 minutes shower the water from the tank will be close to room temperature. Two 10 minute showers close to the water temperature will approach the cold water faucet.

Sound familiar?

3 Likes

Now if the bottom element is burned out, only the upper 8 or 10 inches of water is hot. The rest is room temperature or colder. In an 80 gallon tank the upper element might be 10 or 12 gallons. So with just one person showering, after one 10 minutes shower the water from the tank will be close to room temperature. Two 10 minute showers close to the water temperature will approach the cold water faucet.

Sound familiar?

Not really, because the upstairs shower never runs out of hot water. It takes all the supply away from the lower shower if both on at the same time, and never has a problem with water going tepid or cold. The only trigger for the downstairs shower losing hot water is if someone uses the upstairs one at the same time. They can have back to back use of the downstairs shower with no water temp issues. Or am I misunderstanding?

Great info on water heaters however, so thank you.

IP

1 Like

You’ve probably figured out by now that unless you know the entire layout of the plumbing and the differences, run lengths, the number of pipe bends, constriction points, etc between the two showers, you’re not likely to figure out the issue let alone solve it. In my mind’s eye, the upstairs shower clearly has an easier path for the water to run than the downstairs. Whatever that reason is, it is overwhelming the fact that the water has to go farther and higher than the closer shower – so it gets all the hot water. Just my thoughts. It has nothing to do with the water heater itself.

2 Likes

Whatever that reason is, it is overwhelming the fact that the water has to go farther and higher than the closer shower – so it gets all the hot water. Just my thoughts. It has nothing to do with the water heater itself.

I suspect the only remedy will be an independent tankless water heater for the downstairs…not that there is room even for that.

IP

A tankless heater may require a larger gas line than is available. We looked at getting one when our water heater failed, but the gas line to the water heater location is too small. So we can’t do it without running a new line from the meter to the water heater. Which is totally doable, but more than doubles the price of the replacement (I think it was about 5x, actually).

1poorguy

1 Like

…the upstairs shower clearly has an easier path for the water to run than the downstairs…

That’s what it sounds like, but - if this is a new issue, there’s something else. Unless maybe after all these years, this is the first time both showers were in use simultaneously…

horacekgl: You’ve probably figured out by now that unless you know the entire layout of the plumbing and the differences, run lengths, the number of pipe bends, constriction points, etc between the two showers, you’re not likely to figure out the issue let alone solve it. In my mind’s eye, the upstairs shower clearly has an easier path for the water to run than the downstairs. Whatever that reason is, it is overwhelming the fact that the water has to go farther and higher than the closer shower – so it gets all the hot water. Just my thoughts. It has nothing to do with the water heater itself.

I agree with this. Another cause can be that the pipes to the downstairs are narrower…this could be based on the actual pipe size or they have built up mineral deposits or other partial clog. When this is the only path, water flows. But when water can go to two places it gets very little and the shower mixing valve gets mostly cold water. You can test this if you have a sink faucet that has separate hot and cold valves. Do you get any hot water flow at all? Turn on a downstairs hot valve…you should have some flow, then turn on the upstairs shower…does the hot flow drop much lower?

Mike

OK, starting over.

The most common cause for running out of hot water is a broken dip tube. “New” water is carried down to the bottom of the tank by the dip tube, hot water is pulled from the top of the tank. Replacing a dip tube is easy, but unless you’re comfortable with not having seen it before I’d hire a plumber.

But that doesn’t sound like the problem. Neither is this:

The primary heater for a water heater is the upper element. Since water is pulled from the top of the tank, it’s important that that water be hot. The electricity turns on the upper element first, when the thermostat triggers that it’s hot up there the electricity is re-routed to the lower element to start heating there. The lower element probably runs more, just because hot water rises (just like hot air), but the upper thermostat is the one making the decisions. If that thermostat is broken then nothing happens. If the lower thermostat is broken, the upper one will still function.

But that doesn’t sound like the problem. So here are a couple of speculations:

I would guess the tenant has removed the flow restrictor from his shower, allowing him to pull double, or even more of the flow to his faucet head, starving the one downstairs. Replacing the flow restrictor will not make him happy, but that’s life. You can probably tell the difference between a shower head with and without just by observation.

You might also ask the upstairs tenant if he/she is in the habit of talking half-hour showers and tell him/her to knock it off :wink: Putting an endless flow water heater in line will do nothing except drive your energy costs through the roof.

House plumbing is usually designed with 3/4” pipes feeding the main distributions and 1/2” pipe feeding specific venues like showers, sinks, toilets, etc. (There is ~twice as much flow through the 3/4”). I cannot conceive of a reason a plumber would run 3/4 mains to the second floor and 1/2s to the first, but perhaps the first is a conversion and to save a few bucks on a long run to the “new” bathroom the smaller diameter piping was used. I have no solution to this except to look at the pipes in the basement (if possible) and change them if necessary.

One way to make a tank “bigger” without buying a new tank is to set the thermostats higher on the heating elements. This will get you into “scald” territory, which you then temper down with a thermostatic mixing valve. In fact I just installed one on my heater at the suggestion of someone on this board during a conversation about my solar heating of the water. My plumbing is mostly pex and it took me 15 minutes to do the job. The valve was around $60, iirc. Now my heater sits at 150 degrees, but the mixing valve adds enough cold water when water is pulled to bring it back down to 120. That gives me much more capacity in the same size tank.

Although it’s already been mentioned, it’s not unlikely if this is an older house in a hard water area that some/all of the pipes have gotten narrowed by mineral deposits. Again that would affect the flow and allow one faucet with more open pipes to dominate, even if the path was longer.

Idon’t recall if you mention that the upstairs shower is fine unless the downstairs is running. If it’s not fine at any time then that’s the shower mixing valve or clogged shower head. (Replace is easier, but you can clean with LimeAway or similar). If it only happens when both are running then I’d look into the “restricted flow” argument.

I was replacing a 40 gallon gas water heater and when I looked at a tankless, I was told 1.24 inch gas line and a 6 inch chimney stack.