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Instant hot water tank cycles when using sprinklers

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  • May 25th, 2020 10:24 am
[OP]
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Nov 28, 2016
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Instant hot water tank cycles when using sprinklers

So adjusting my timer on my sprinklers and testing them, and first I thought it was just a coincidence, maybe someone was washing their hands or something at the same time

But everytime I turn on my sprinklers (I do it manually) my instant hot water tank cycles. When other cold taps are run, it doesn't

Does it have to do with the size of the sprinkler line? As in since its a lot larger to the outside then the regular cold lines, is it because of pressure difference in the line due to the size?

Ive tested it many times, alone in the house, and no matter what, I hear my tank cycle, with no other taps on in the house.

And its defintly not the sprinkers are tied into the hot water at all (I have heard people that have made that mistake), the hot is all a separate bank not linked to the sprinklers at all

The T to the cold water feed to the tank off the main is before the sprinkler as well.
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Deal Addict
Dec 17, 2007
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Alliston, ON
Is the water flowing backwards through the hot water tank causing it to see flow and cycle? Maybe you need a check valve on the cold water inlet of the tankless water heater so water can only flow into the unit and not in reverse through ut
[OP]
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Nov 28, 2016
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schade wrote: Is the water flowing backwards through the hot water tank causing it to see flow and cycle? Maybe you need a check valve on the cold water inlet of the tankless water heater so water can only flow into the unit and not in reverse through ut
Im not sure, how would I check that? Im new to these things. There is defintly not a check valve on it. I do have one on the sprinkler line however so it wont backflow into the house plumbing
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Dec 17, 2007
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WikkiWikki wrote: Im not sure, how would I check that? Im new to these things. There is defintly not a check valve on it. I do have one on the sprinkler line however so it wont backflow into the house plumbing
Is there a shut valve on the lines going in and out of the tankless unit? Shut them off and see
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schade wrote: Is there a shut valve on the lines going in and out of the tankless unit? Shut them off and see
Yes there is, Ill test it later. House is full and rather be home alone so I know no one is turning on faucets etc

If it is what you suggest, is that hard on the tank? Not that I will leave it, Ive only used the sprinklers 3 times this year so far.
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Well its just not the sprinklers. Using an outside faucet today, no one was home, and since its on the same side of the house, I hear the hot water tank exhausting. Go there and its blowing out exhaust. It quits after a bit

I did the test of turning off the bypass and the using the sprinklers. The tank does not cycle at all

I took the fron off ands its definitely the blower fan exhausting. Its not firing NG though. I tested with a tap full on hot and I see the flame in the small check window just to see the difference

It also cycles sometimes with more testing when the cold it turned off to it seems as well
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Oct 12, 2007
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I assume you're talking about one of those hot water recirculation set-ups and not a "tankless water heater". If so, you may find that the outside hose bibbs are connected more directly to your water supply (whether municipal or well) and they run a lot colder than cold water faucets do. Plus, they run a lot more volume of water - therefore, very cold. Few people when washing their hands run enough water to make the water (and the pipes) really cold. But an external hose bibb will absolutely get cold.

So, check to see if those cold water pipes are close enough to your hot water pipes to cool down neighbouring pipes, dropping the temperature enough to trigger the recirculation pump. Other than insulating the pipes, I can't think of a good solution.
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May 23, 2009
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Mississauga
I recall you got it installed recently. Did they use your cold water lines to create a recirculation loop?
[OP]
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CaptSmethwick wrote: I assume you're talking about one of those hot water recirculation set-ups and not a "tankless water heater". If so, you may find that the outside hose bibbs are connected more directly to your water supply (whether municipal or well) and they run a lot colder than cold water faucets do. Plus, they run a lot more volume of water - therefore, very cold. Few people when washing their hands run enough water to make the water (and the pipes) really cold. But an external hose bibb will absolutely get cold.

So, check to see if those cold water pipes are close enough to your hot water pipes to cool down neighbouring pipes, dropping the temperature enough to trigger the recirculation pump. Other than insulating the pipes, I can't think of a good solution.
No Im not, Im talking about a "tankless water heater" I don't have a recirculation pump.

My outside bib is connected to the same manifold as the rest of my cold water lines for the house, same size. The only one that is not on the manifold is the sprinkler system, which is right off the main water line
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bubuski wrote: I recall you got it installed recently. Did they use your cold water lines to create a recirculation loop?
Ill be honest, I have no idea what you mean. They used the line that was going into the old hot water tank, just extended it for location.

I contacted Noritz directly about it, just waiting to hear an answer. To me its just unnecessary use and wear and tear on the unit, if the blower fan turns on each time the cold is used. Extra power as well
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May 23, 2009
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Mississauga
It's an unlikely situation but the issue you are having is pretty odd. What I gathered is that sometimes when you use a cold water faucet your tankless senses water flow activates.

One explanation could be a faulty crossover valve. They are pretty unreliable but really the only way to do a retrofit tankless recirculation loop. It is simply a way to get hot water quicker at the faucets far away from the tankless.
Image

The re-circulation feature is sort of explained here on Nortitz website and your installer may or may not have activated the feature. Does your model have built-in a pump?
https://www.noritz.com/tankless-recirculation/
[OP]
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Nov 28, 2016
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bubuski wrote: It's an unlikely situation but the issue you are having is pretty odd. What I gathered is that sometimes when you use a cold water faucet your tankless senses water flow activates.

One explanation could be a faulty crossover valve. They are pretty unreliable but really the only way to do a retrofit tankless recirculation loop. It is simply a way to get hot water quicker at the faucets far away from the tankless.
Image

The re-circulation feature is sort of explained here on Nortitz website and your installer may or may not have activated the feature. Does your model have built-in a pump?
https://www.noritz.com/tankless-recirculation/
Happens when just cold is used, as in my outside tap, is cold only. There is no crossover valve. Yes all of my sinks and showers are single handle. so I have them at multiple locations. But I doubt I have them ALL faulty to let hot water through

Sprinklers and outside spigots are cold water only, and it still happens

Id like to a recirculation for the house. Washing hands its always with cold water. Because it takes so long for hot water to get to the sink, I just don't bother even turning on the hot. Unless its for dishes or something and you are filling the sink or something
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May 23, 2009
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Only one crossover valve is installed in each setup and does not matter if your sinks and showers are single handle.

For example using my crude image below, let assume a crossover valve is installed under your kitchen sink to serve your whole household, lets also assume it fails and starts working intermittently(even a faulty faucet cartridge).
When you use your outside spigot, the water will be flowing using the path of the orange arrow through the crossover valve under the kitchen sink instead of the green arrow which comes directly from the city.
One way to confirm is to wait and see if the water coming out of the outdoor spigot or sprinkler eventually turn warm. It should when all the cold water in your indoor lines run out.
Images
  • crossover.png
[OP]
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Nov 28, 2016
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Out west
bubuski wrote: Only one crossover valve is installed in each setup and does not matter if your sinks and showers are single handle.

For example using my crude image below, let assume a crossover valve is installed under your kitchen sink to serve your whole household, lets also assume it fails and starts working intermittently(even a faulty faucet cartridge).
When you use your outside spigot, the water will be flowing using the path of the orange arrow through the crossover valve under the kitchen sink instead of the green arrow which comes directly from the city.
One way to confirm is to wait and see if the water coming out of the outdoor spigot or sprinkler eventually turn warm. It should when all the cold water in your indoor lines run out.
Then I have no cross over valves, because under my sinks the hot and cold line go up seperatly to the fixture. The only "crossover" would be in the handle itself, sink or shower (unless Im misunderstanding what you mean)

How can a single line spigot cold only, be stealing hot water from another line? Its a straight run from the manifold to the spigot, same as the sprinklers. The hot water is no way linked to that line. Hot water manifold and cold water are separate (as they should be) There is no possibility of "cross talk" so to speak
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Dec 17, 2007
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Alliston, ON
It could be the high flow of the exterior tap or the irrigation that is working like a siphon and pulling the water from the hot water unit. Try only opening the outside tap a 1/4 of the way and see if the same happens. Most taps in your house might be 1-2gpm but your outside hose bib or irrigation could be much higher.

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