# Another hot/cold cross connection issue



## knuckles (Dec 16, 2011)

Looking for some input.

We take care of the HVAC and plumbing in a 32 story apartment building. One tenant complains of getting only hot water out of his cold water taps.
the issue seems to happen occasionally through out the day. This guy wakes up at 1am and cant get cold out of his faucet.

The building is broken up into 8 sets of risers. Each riser serves 2 units per floor. The building is also broken into 3 pressure zones. 
Low pressure is Basement to 7th floor.
Med pressure is 8th to 20th floor.
High pressure is fed down from the roof, 32nd floor down to 21 floor.

The tenant is on the 20th floor and only has about 25-30 psi at his unit. He is at the top of the Med Pressure zone.

He is the only one complaining of this issue.

I have replace the shower cartridges is his space and his nieghbors space just to be sure. But while testing i found that the cold water main serving his apartment got warmer as i ran water. I cant find the cause and cant find any mop sinks or anything else.

One thing to add is that every unit has a insta hot connected to the cold.

Any ideas or things to check?


----------



## moonlighter (Sep 29, 2012)

Does anyone on that riser have a portable dishwasher hooked up to kitchen sink or a personal shower wand that they leave the faucet on in the shower and use the shut off on the wand itself I have run in to that more times than I can count but to find it is gonna take some time do to the number of units


----------



## Gettinit (May 9, 2012)

The source of your problem should be very close.


----------



## knuckles (Dec 16, 2011)

I have a guy going into each apt on the riser and disconnecting the insta hots. While he's in there I'll have him look for anything that's not original to the apartment. My guess is that the issue is in a unit near by but they have not complained. 
This is a expensive apartment building downtown.


----------



## BROOKLYN\PLUMB (May 21, 2010)

knuckles said:


> I have a guy going into each apt on the riser and disconnecting the insta hots. While he's in there I'll have him look for anything that's not original to the apartment. My guess is that the issue is in a unit near by but they have not complained.
> This is a expensive apartment building downtown.


Insta hots only heat the water on demand and unless it's somehow connected to hot and cold you can't have a cross connection there. 

How is the water being heated? Is he the only one on that riser with this problem? 

If there's a mixing valve it should be piped with a heat trap


----------



## bjmi007 (Apr 28, 2012)

*i run into similar problem u have.*

My problem with the hoa unit about 5 unit all connect to each other, the first unit turn on cold water they get hot water, sometime it cold for a few second and go hot and sometime it cold again, its on a boiler system feed 5 unit but one boiler feed them all, seem like the first unit have this problem only, the other unit dont complaint, i turn on the spigot right at the front of house where u shut off water to the hole house i get hot water right away, i trace it back to the boiler found a check valve, i suppect it is check valve we put a bid to replace but they didnt go for it, so back to ur problem check for a check valve gone bad if u got one.


----------



## knuckles (Dec 16, 2011)

BROOKLYN\PLUMB said:


> Insta hots only heat the water on demand and unless it's somehow connected to hot and cold you can't have a cross connection there.
> 
> How is the water being heated? Is he the only one on that riser with this problem?
> 
> If there's a mixing valve it should be piped with a heat trap


Water is heated on the 7th floor with two boilers and a 500 gallon storage tank. The affected riser is almost the farthest from the heating source. As in there are 3 other risers between the boiler and the affected area.

The only thing im thinking with the insta hots is possibly not shutting off. I have seen steam out of insta hots before.


----------



## Nealfromjpt (Oct 10, 2012)

is there a return loop on the storage tanks?, if so , maybe a check valve? , maybe a check valve (if Equipped) on the insta hots?


----------

