Water heaters in series water is not equally hot thruout the house

[wddossett]

Hi, I am no plumber - I just moved into a new house and I have the problem in the subject. I have two 40 gallon Rheem water heaters 5 yrs old. They are cranked up nearly as high as they go... some faucets get pretty hot, some are just warm. I believe the water heaters are plumbed in series as cold water goes into the bottome of one of them. Then they are interconnected at the top by two pipes... but as far as I can tell, both of these pipes on the top are also feeding the house... so I would think the cold water would go to one water heater, then that heater would go to the second and that would supply the house. I have attached some pics, first one shows the single cold water feed at the bottom, 2nd one is the two interconnects on top of the tanks and both interconnects are feeding up into the house.




So I had a plumber out yesterday, and he was trying to tell me what was going on, saying it shouldn't work, or the check valve is bad etc etc and honestly kind of lost the plot eventually and he turned the heaters down, said he would call me and to them tell him if it made any difference. He didn't call yet, but we don't have as much hot water now, so worse than before.

There are just two of us in the house, we do take baths, its not a huge tub (small compared to our last house, we lost that in the Colorado Marshal Wildfire and pretty sure that was plumbed in parallel). Seems like forums and posts I have been reading parallel has a slight lead - makes sense to me... but then some say the heaters don't feed evenly. These are identical heaters installed at the same time...

So, I am not a plumber as stated... I am pretty technical and do all my own electrical work and building work - I've only just started learning plumbing as I need it. So, advice? and what would it take to plumb these in parallel? Just a cold water feed at the bottom of the other tank, with the way they are plumbed at the top, it looks to me like this it is plumbed half and half or something. Also the cold water feed to the bottom of one tank, the pipe is warm if that makes any difference, is that problem with the check valve?

Sorry for being such a newb, but feel like I need a primer before talking to the plumber, I am not going to attempt this myself, just want to understand what they are saying - oh. yeah, he said there was like a cold water layer somewhere or something that was not making one of the tanks feed or something.

Thanks, really appreciate any advice for a layman to understand here.

Bill

 

[wddossett]

oh and just a note, I am pretty sure that the showers are not getting as hot as we like as I need to adjust the mixer on them, but there is a not water faucet, almost directly above the water heaters - I turned off the cold into the mixer and it still only runs warm while a faucet on the other side of the house is nice and hot.

 

[Twowaxhack]

It’s not piped in series. The swing check at the bottom shouldn’t be laid on its side. I would discontinue the piping at the bottom of you don’t have a circulating system.

Looks like an improper parallel piping install.

You need to pipe the cold water to the first water heaters cold inlet. Then connect the hot water out of that heater to the cold water of the second heater. The hot water out of the second heater goes to the house fixtures. It’s called series piping.

Then remove the piping at the bottom all together if there’s no circulating hot water system.

 

[wddossett]

thanks, I am learning now.

There is a circulating system. I followed the wrong pipe going to the base of the water heater. I kept wondering why the water was warm out of the faucet in the master bath so quickly - just assumed wife had been running hot water in the bathroom. I know even less about circulating systems other than they circulate warm water so you get warm water to further away parts of the system quickly. I like that.

So, the question then is why do the heaters have to be turned up so high to get reasonably warm water? Would the check valve being on its side cause that? or what would be results of that? And why am I not getting hot water equally to all parts of the house, even after running water for like 10 minutes on some faucets?

Hopefully will hear back from the plumber today.

Thanks again for advice, I just like to confirm what is wrong and needs to be done.

It’s not piped in series. The swing check at the bottom shouldn’t be laid on its side. I would discontinue the piping at the bottom of you don’t have a circulating system.

Looks like an improper parallel piping install.

You need to pipe the cold water to the first water heaters cold inlet. Then connect the hot water out of that heater to the cold water of the second heater. The hot water out of the second heater goes to the house fixtures. It’s called series piping.

Then remove the piping at the bottom all together if there’s no circulating hot water system.

 

[Twowaxhack]

The check valve should be replaced and turned to its upright position.

The parallel piping should be corrected and I think the easiest way for you to do that would be just changing to series piping.

I believe you’re getting water back flowing through your check valve at the bottom. This will cause erratic temps and complaints for no hot water. Replace that gate valve to a ballvalve.

 

[Ars Glonalin]

KISS! Ok, Keep It Simple Sir.

Tests and results. Given that you can't see all of the runs through the walls, best to try to understand what's going on. Devise tests that can help you do that. The right question contains most of the answer. So,
1. Can you shut off the circulating system temporarily, by valve switch or pump? (Circulation needs to be off for all steps below unless indicated.)
2. Then wait a day (more in warm weather.)
3. Turn on a faucet that hasn been used all day but would normally only get warm watet. Catch and then take temperature of the first 1/2 gallon. Let it run for 5 minutes. Capture another 1/2 gallon. Take its temp. If it went up, let it run for 5 more minutes. Did it go up more? (During test be sure no other outlet is consuming water.
4. Do you have access to the hot water pipes between heaters and far outlet? If you do, then run hot and feel them....
5. Try turning off hot-out valve at water heater(s) and then run hot water at remote outlet. If hot runs at the remote outlet, it should never get warm as it's supplied with cold water.
6. What test can you perform to ascertain whether the circulation system is the only way some remote faucet/fixture is supplied with hot?
7. For series, cold water goes in top of heater 1, comes out top of 1 warm/hot and goes in top of heater 2 as the 'cold' or intake, then should come out of top of heater 2 as the only hot supply line to normal plumbing system.
8. A corculation system could be engineered to come from the top of either heater.
9. A parallel system splits intake: cold water from supply to top of heater 1 and heater 2 (a 'y' or a 't' or a manifold of cold water supply.) Then hot water from the top of both tanks is combined (y, t or manifold), possibly with backflow checkvalves, as hot-out to the plumbing system.
10. If cold water goes into heaters 1 & 2, and their hot-out goes to different outlets they are separate systems.

Mental math....

 

[Twowaxhack]

For keeping it simple that sure is a lot of crap.

 

[wddossett]

lol - thanks, I think I can at least talk to the plumber about how we are going to fix this now... one last question though from the last post, if there is, and there seems to be a circulation system, is there a pump somewhere? or can it just circulate by hot water expansion? I haven't seen a pump anywhere so far anyway.

For keeping it simple that sure is a lot of crap.

 

[Twowaxhack]

There are thermosiphon systems that do not use a pump.

The first thing I suggest you do is replace the gate valve at the bottom with a ballvalve. Then close it.

Then test the system for a good hot water temp at the outlets.

Then we will go from there.....

 

[wddossett]

Hi, sorry, had some other stuff going on... I presume you want me to replace the gate valve as they are crap and will fail eventually... this one is actually fairly new and closed off ok, but yeah, last time I tried to close one on my old system the hendle came off in my hand and I replaced all with ball valves. Anyhoo, I closed it and I am now getting hot water to all of the faucets in the house, some take 2 or 3 minutes, but I don't mind that, at least they are all hot.

So I am guessing this circulating system isn't really working or something - I can live without that - should I just replace the valve when I have time to drain down the system and close it and leave it like that? Or should I remove the plumbing going into the bottom of the tank altogether and just cap that pipe off?

Thanks again, this is much better, I am going to turn the water heaters down now and see what I can run them at to get hot water and not cranked up to their highest settiong.

 

[MrInfoPhilly]

Hi, sorry, had some other stuff going on... I presume you want me to replace the gate valve as they are crap and will fail eventually... this one is actually fairly new and closed off ok, but yeah, last time I tried to close one on my old system the hendle came off in my hand and I replaced all with ball valves. Anyhoo, I closed it and I am now getting hot water to all of the faucets in the house, some take 2 or 3 minutes, but I don't mind that, at least they are all hot.

So I am guessing this circulating system isn't really working or something - I can live without that - should I just replace the valve when I have time to drain down the system and close it and leave it like that? Or should I remove the plumbing going into the bottom of the tank altogether and just cap that pipe off?

Thanks again, this is much better, I am going to turn the water heaters down now and see what I can run them at to get hot water and not cranked up to their highest settiong.

Simple answer is you need a good plumber that has proper understanding on hot water systems and circulating hot water.
I don't see why you need 2 40 gallon water heaters.
How many bedrooms and bathrooms? you have 5 full bathrooms or something, 2 large full families?

As I would've advised you to go with a 50 gallon water heater with a HIGHER 1st Hour rating such as GCG-50 - AO Smith GCG-50 - 50 Gallon ProLine 6 Yr Warranty Residential Gas Water Heater - Tall Model
Water Heaters are based on First hour rating! That one I gave you has a rating of 88 gallon first hour rating
So for 3.5 Bathroom 6 bedroom house you need at least 80 Gallon First hour rating., So the 1 water heater linked is significant.
Then if your system is piped correctly with your circulator., Which I would've tied it into the Cold Feed line to the water heaters with a check valve., You would NEVER run out of hot water., under normal use.

 

[Twowaxhack]

First hour rating doesn’t work for me.

If I have two kids taking showers and then I want to take a shower when they get finished, it doesn’t help me that the water heater can heat 40 gallons of water in 30 minutes. I need hot water now......

I size heaters based off expected use.

A tankless heater shines in the above scenario.

 

[wddossett]

Yeah, me and good plumbers seem to be a jinx. I call and they never call back.. they are all too busy I guess. Saying that, I turned off the gate valve on the pipe going into the bottom of the water heater and have been turning down the dials on the water heaters so they are only at the normal arrow, setting now and we have hot water everywhere. And I swear the circulator is working as well as the bathroom in the master bath has hot water to the sink in like 2 seconds... I mean it isn't far from the heater, maybe 25 feet.... but all in all, everything seems to be working fine now. I'm only in this house for 2 yeas and then selling it. It has 3 full baths, 4100sq ft and 5 bedrooms... also has a kitchen in the basement so that could be a separate renal unit or something, so I am not changing anything out on the water heaters. I would LOVE to have a plumber explain to me how the circulating system is or is not working and why that was piped into the bottom of the waterheater. I have a clue as to who may have done it, large plumbing firm here in colorado with not a great rep, so might give them a call to see if they possibly did it and can explain how it works... or more precisely wasn't working before I turned that valve off. And I am going to replace that gate valve and a few others in the house with ball valves.

 

[MrInfoPhilly]

First hour rating doesn’t work for me.

If I have two kids taking showers and then I want to take a shower when they get finished, it doesn’t help me that the water heater can heat 40 gallons of water in 30 minutes. I need hot water now......

I size heaters based off expected use.

A tankless heater shines in the above scenario.

I strongly disagree., there are some 50 gallon tanks I've installed that will supply more hot water than 75 gallon tanks per hour.

Hot water duty cycle is based off of btu, and design. It's no way you're using only hot water in the shower., so 30 minute shower is not using only the hot side. You're mixing the hot water with the cold. And if the tank is set around 140°F your showers are likely around 105 to 110, you wouldn't be running out of hot water.

In my house we all take back to back showers and no issue.
I'll take a tank over tankless anyday. Once the water is warmed, its stored.
Better than from cold to hot., plus you can have the recirculation with a tank.

 

[MrInfoPhilly]

Yeah, me and good plumbers seem to be a jinx. I call and they never call back.. they are all too busy I guess. Saying that, I turned off the gate valve on the pipe going into the bottom of the water heater and have been turning down the dials on the water heaters so they are only at the normal arrow, setting now and we have hot water everywhere. And I swear the circulator is working as well as the bathroom in the master bath has hot water to the sink in like 2 seconds... I mean it isn't far from the heater, maybe 25 feet.... but all in all, everything seems to be working fine now. I'm only in this house for 2 yeas and then selling it. It has 3 full baths, 4100sq ft and 5 bedrooms... also has a kitchen in the basement so that could be a separate renal unit or something, so I am not changing anything out on the water heaters. I would LOVE to have a plumber explain to me how the circulating system is or is not working and why that was piped into the bottom of the waterheater. I have a clue as to who may have done it, large plumbing firm here in colorado with not a great rep, so might give them a call to see if they possibly did it and can explain how it works... or more precisely wasn't working before I turned that valve off. And I am going to replace that gate valve and a few others in the house with ball valves.

Maybe this weekend we can video chat and I'll walk you thru it

 

[Twowaxhack]

I strongly disagree., there are some 50 gallon tanks I've installed that will supply more hot water than 75 gallon tanks per hour.

Hot water duty cycle is based off of btu, and design. It's no way you're using only hot water in the shower., so 30 minute shower is not using only the hot side. You're mixing the hot water with the cold. And if the tank is set around 140°F your showers are likely around 105 to 110, you wouldn't be running out of hot water.

In my house we all take back to back showers and no issue.
I'll take a tank over tankless anyday. Once the water is warmed, its stored.
Better than from cold to hot., plus you can have the recirculation with a tank.

You can disagree but I assure you that 2 teenage girls empty a 50 gallon gas and the 3rd person is going to run out of hot water. Typical BTU is 38-50k for residential gas.

So first hour doesn’t matter when I can deplete the 50 gal tank in 20 minutes or less. It’s pretty simple snd you’re not considering flow rate. My showers might use more water than yours. We might be filling up a 75 gal garden tub.

You can have circulation with a tankless.

 

[Twowaxhack]

Two teenage girls who take 15 minute showers with a shower head volume of 3gpm and a water heater setting of 140 and a cold inlet of 60 degrees and a mixed shower temp of 105 degrees will use 56% hot water. That’s 1.68 gpm of hot water.

15 minutes x 1.68 gallons per minute of hot water = 25.2 gallons of hot water.

Your 50 gallon wouldn’t give me two showers..........

 

[MrInfoPhilly]

Two teenage girls who take 15 minute showers with a shower head volume of 3gpm and a water heater setting of 140 and a cold inlet of 60 degrees and a mixed shower temp of 105 degrees will use 56% hot water. That’s 1.68 gpm of hot water.

15 minutes x 1.68 gallons per minute of hot water = 25.2 gallons of hot water.

Your 50 gallon wouldn’t give me two showers..........

The heater I listed in the link-
https://www.supplyhouse.com/AO-Smit...ranty-Residential-Gas-Water-Heater-Tall-Model
50 Gallon Hot water tank
40,000 BTU Gas
1 hour rating 88gal
90F degree rise 41 gph KEY number (based on about 62F water)
excellent., lets do math... Bit tired so I do the Math equations on next post. But you're forgetting part of the equation. The Recovery part. Your math holds true for a STORAGE Tank of hot water.

408.2 Water Consumption. Showerheads shall have a maximum flow rate of not more than 2.5 gpm at 80 psi

So lets rate at the max flow., assuming you have 80psi and 2.5 gpm shower heads
@ 15minutes each thats 37.5 gallons of water total.
each person uses about 21 Gallons of Hot Water Per use.
we will keep the percentages simple as u did.
56% hot water used=21 GPH (0.35 gpm) of hot water used per person

Now the water Heater I listed recovers at a rate of rounded up to 0.70 GPM(about0.683) gpm hot water.
0.70 GPM is bigger than your daughter using 0.35 GPM

So the hot water tank is actually recovering faster than your daughters are using it based on 140 degree setting at the hot water Tank

Let me know If I missed Calculated.

 

[Twowaxhack]

The recovery is not keeping up with the demand. Not by far.

I have two showers running simultaneously at 3.0 gpm with 1.68 gpm being 140 degree water. 1.68 x 2 showers = 3.36 gpm. 3.36gpm x 15 minute shower = 50.4 gallons of hot water in 15 minutes.

The water heater you posted can’t deliver 50.4 gallons of thermostat setting water in 15 minutes. And if it could I would only get two showers........

A 50 gal. 40k btu water heater can’t deliver 50.4 gallons of thermostat setting hot water in 15 minutes with typical cold water temps.

It’s 2.5gpm per showerhead, not per shower. Correct ? Showers are not limited to one head.

 

[Twowaxhack]

The heater I listed in the link-
https://www.supplyhouse.com/AO-Smit...ranty-Residential-Gas-Water-Heater-Tall-Model
50 Gallon Hot water tank
40,000 BTU Gas
1 hour rating 88gal
90F degree rise 41 gph KEY number (based on about 62F water)
excellent., lets do math... Bit tired so I do the Math equations on next post. But you're forgetting part of the equation. The Recovery part. Your math holds true for a STORAGE Tank of hot water.

408.2 Water Consumption. Showerheads shall have a maximum flow rate of not more than 2.5 gpm at 80 psi

So lets rate at the max flow., assuming you have 80psi and 2.5 gpm shower heads
@ 15minutes each thats 37.5 gallons of water total.
each person uses about 21 Gallons of Hot Water Per use.
we will keep the percentages simple as u did.
56% hot water used=21 GPH (0.35 gpm) of hot water used per person

Now the water Heater I listed recovers at a rate of rounded up to 0.70 GPM(about0.683) gpm hot water.
0.70 GPM is bigger than your daughter using 0.35 GPM

So the hot water tank is actually recovering faster than your daughters are using it based on 140 degree setting at the hot water Tank

Let me know If I missed Calculated.

You miscalculated. 56% of 2.5gpm is 1.4gpm. Not .35gpm.