The hot water tank is fairly new and I would not guess that sediment is clogging the line. Tenant reports she has noted that part of the floor has seemed warmer than other areas for as long as she has been living there. I spoke with someone who suggested there is a slab leak. There is a cement foundation. Does this make any sense with regard to the lack of hot water coming from all the showers and faucets in the house? To me, it seems like there is more an issue with the tank. --76.183.xxx.xxx

Another simple test is to swap hot and cold water lines temporarily at the water heater (easy if you have flex hoses but difficult if you have hard copper) and see if this moves the issue to the cold water side. --99.92.xxx.xxx

How old is the hot water heater, to me that’s an issue with the hot water heater. This happened to a friend of mine and his tank was only 4 years old. As far as a leak under the slab, it would have to be a major leak!! You could run multiple faucets at the same time before this was an issue correct? So it would have to be a major break to cause you to lose pressure like that. Plus I’ve never seen a hot water line run out of a water heater and go under a slab, makes no sense. The main supply from the street maybe, but not after the water heater. Like Hoosier said, need more info. But based on what you said only, my bet it’s with the water heater. Even “newer” water heaters fail, especially if you have high line scale or calcium in the water. --71.248.xxx.xxx

Since it happens at all of the HW outlets, it must be a problem somewhere between where the water enters the heater and the first faucet. I would check the water supply shut off valve where the cold water enters the tank as well as the shut off valve (if there is one) that controls the HW entering the rest of the system. It's common for the washers in shut off valves to come loose or even deteriorate over time. This can allow pieces of rubber to disrupt the flow of water thru the valve or to become lodged down stream. This is just one of the reasons that I prefer to use quarter turn ball valves instead of the older style washer type valves. --96.237.xx.xx

Could the make up water going into the tank not be flowing full stream, - it trickles in, fills up and when used does not recover as fast as used. --108.4.xxx.xx

If there is a leak under the slab, you will have to address it without delays. --99.59.x.xxx

Do you have one of those gadgets in the line that shuts off the water if the temperature is too hot? I had to get them here in NJ. I forget what they are called. Some are right in the faucet I think and there is one right over the hot water heater at one place. Check the water temp setting at the water heater and put it where your state allows it to be set. Plumber will know. --173.61.xxx.xx

your water tank drip tube may be defective in water heater -- if it's all hot faucets in the house. --99.103.xxx.xxx

Myob meant "dip" tube. --24.20.xxx.xxx

darn spell check!!!! --99.103.xxx.xxx

As Hoosier asked - more info needed. Two possibilities. Our home has domestic hot water, ie it comes from our oil fired furnace. There's a coil in the furnace that produces HW. The pressure slowed considerably over years at all faucets. There was an apparent lime/calcium build-up in the HW coil. I went to you tube and learned a technique to "loop" white vinegar through the coil to cleanout the lime/calcium. It worked great - WH runs fine. Unlike JKJ I live in a neighborhood of slab (no basement) homes. Both hot and cold water lines run in or under the slabs. A few years ago, our neighbor discovered a leak under their slab. A plumber with a jackhammer corrected the problem. --73.215.xxx.xx

OP here. Just a follow-up. We sent out a plumber. He said it's definitely not a slab leak. It was a malfunctioning WAGS valve. Hot water is restored. Thank you all for your suggestions. --76.183.xxx.xxx