High rise domestic water problem.

[hvacmike]

I have a 10 story high rise that i am have problems with. I am having cold water feeding into my hot water, causing showers and bathrooms to only have warm water.

I have found my delta p across hot and cold to vary from 4 psig to 13 psig, with my cold water having the higher pressure.

I believe this is my problem but before i start installing pressure regulators in the cold water feeds to these apts i just want to verify i am right.

My cold water feed into the building goes into the building booster pumps before it feeds the building and i am not sure from there where it goes.

Thanks.

[Caduceus]

If this is a new problem and has not occurred in the past you may want to start looking for a backflow device that may be bad. How does the building supply hot water to each unit? Could the problem be there?
With a 10 story building do you have a holding tank/pressure tank in the penthouse?
Without being there this may be a tough one to figure out over the internet. Do a little more investigating and get back to us.

[LiQuId]

I agree with caduceus here, and more info would help.

where is the mechanical room? draw your system out and then ask yourself if there is a chance a prv is faulty in a downfeed cold riser?,