# Irrigation leads to hot water issue



## pigskin plumber (Oct 2, 2011)

I've been doing take offs this year on the regular with no issues, except for one house. Their irrigation comes on early morn before they wake. When they get up and turn the hot water on it looses pressure to almost a trickle, bangs, and comes full flow. (no problems with cold) 

- I changed the dual check and still issue. 

They also say it only happens after the irrigation has cycled on and complete. I was thinking maybe obstruction in hwt, but if it only happens after irrigation is on then wtf?

fyi - I teed off close to the meter, all 3/4, with shut off, then check valve before it exits the house.


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## ShtRnsdownhill (Jan 13, 2016)

sounds like the hot water is being siphoned out of the heater some how and then it takes the mentioned time to refill and get hot water to the faucet...maybe try a check valve on the cold water side of heater, could be a leak in the hot water some where that allows it to siphon, is the water heater lower or higher than the outside ground?


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## OpenSights (Mar 23, 2015)

ShtRnsdownhill said:


> sounds like the hot water is being siphoned out of the heater some how and then it takes the mentioned time to refill and get hot water to the faucet...maybe try a check valve on the cold water side of heater, could be a leak in the hot water some where that allows it to siphon, is the water heater lower or higher than the outside ground?


^^^ this, or there’s a cross connection somewhere. Bad single handle faucet cartridge?

I spent two weeks once investigating this issue once. Turned out the HO had made a dog washing station by his sump crock years ago creating a mixing valve. When I finally figured it out it was a forehead slapper for him.

All honesty, he was getting pissed after the first week of lukewarm water. My moment of joy was when he realized it was all his fault. Good long time customer.


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## Alan (Jun 18, 2008)

Are you the one who installed the irrigation?


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## exclamation (Mar 11, 2013)

I wouldn’t think crossed lines or single handle/press bal carts would cause this - I’ve always seen those do nothing to pressure but just cause warm or cold from hot outlets


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## Tommy plumber (Feb 19, 2010)

The irrigation system would not logically cause a problem with the flow of hot water {this assumes that the incoming pressure is adequate to begin with}. 


I would do a pressure test on the cold with irrigation on; cold with irrigation off; hot with irrigation on; and finally hot with irrigation off. 
See what the pressure readings are.


Then go from there. 
If that all checks out, then start examining at and around the W/H.


In my humble opinion.


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## OpenSights (Mar 23, 2015)

Another question, one or two meeters? What’s the feed? How are they hooked up?


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## canuck92 (Apr 1, 2016)

Thermal migration, undersized water piping, is it copper or plastic ?


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## OpenSights (Mar 23, 2015)

My bet is still some sort of mixing valve. Single handle valve cog. Takes some time, but easy to find the offender.


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## exclamation (Mar 11, 2013)

OpenSights said:


> My bet is still some sort of mixing valve. Single handle valve cog. Takes some time, but easy to find the offender.


Yea maybe that or an old press bal cart just acting up - I was assuming it’s the whole house with low hot press and thinking in my earlier post in the crossover sense of acting up, which I wouldn’t think would be the case, but indeed maybe some clog in a cart or sticky press bal - is it low pressure for the whole house or just one place/tub+showers only?


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## Fatpat (Nov 1, 2015)

The hot water feed at the top of the water heater is stopped up.

If you ran the cold at every fixture in the house (excluding the irrigation)

I bet you would have the same symptoms, a cross connection would not materialize as low water volume.


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## Tango (Jan 13, 2018)

Maybe you got something stuck in there? Water heater Cold/Hot 2 weeks ago. First time I see that.


.


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## ShtRnsdownhill (Jan 13, 2016)

I dont think a blockage on the water heater is the issue, the water heater sounds like it is being drained, then takes time to refill and have pressure then a good woosh when the hot water and air purge from the faucet, so I would check water pressure and volume and see if there is an issue there...is main valve full open? any more info from the OP?


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## Alan (Jun 18, 2008)

I don't think it's been clarified whether this is a whole house issue or if they are just experiencing it at a single fixture or bathroom.

Single fixture issue would probably be a no brainer.

If not can you duplicate the issue without any trouble? Multiple times of day?

Water heater inlet check valve? Maybe it's sticking shut, pressure on hot side drops enough, irrigation system shuts off, bang : water hammer, check valve open.


:vs_cool:


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## pigskin plumber (Oct 2, 2011)

No, irrigation company. They are pretty good too.


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## pigskin plumber (Oct 2, 2011)

ShtRnsdownhill said:


> I dont think a blockage on the water heater is the issue, the water heater sounds like it is being drained, then takes time to refill and have pressure then a good woosh when the hot water and air purge from the faucet, so I would check water pressure and volume and see if there is an issue there...is main valve full open? any more info from the OP?


Yes, valve is fully open


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## pigskin plumber (Oct 2, 2011)

Fatpat said:


> The hot water feed at the top of the water heater is stopped up.
> 
> If you ran the cold at every fixture in the house (excluding the irrigation)
> 
> I bet you would have the same symptoms, a cross connection would not materialize as low water volume.


okay I will give that a try


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## pigskin plumber (Oct 2, 2011)

Alan said:


> Are you the one who installed the irrigation?


No irrigation company


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## ShtRnsdownhill (Jan 13, 2016)

pigskin plumber said:


> Yes, valve is fully open


did this problem start when the sprinkler system was installed or did it just start at some point and time?


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## Tango (Jan 13, 2018)

Deleted


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