We've just moved into a new house. It is in great shape. We just replaced the 22 year old water tank with a 50 gal Rheem. With the old tank or the new one we can't seem to get hot water to the sinks and showers. If we let the water run it may take 15 minutes for the temp to begin to change. The plumber that did the tank install says it's probably because the hot and cold water pipes are running too close to each other. We have radiant floors so there must be water flowing through the slab before it gets to the faucets and showers further away from the tank. So this plumber made sense to me but now we've discovered that if you turn the water off and on until you hear what seems like 'water hammer'. The hot water comes through in seconds. Once the shower upstairs gets hot water all the faucets in the house start get hot water. It only works with the shower as I can't get the same effect on the sinks. So now I think the pipes are fine and maybe there is overly high cold water pressure? Any ideas? :(

Please help the dewd!

Is there a check valve on the cold water supply to the tank? Let me know, Tom

Answer Tom's question as a check valve issue could definitely cause this issue. Another thing is to look around for a recirculating pump... sounds like the pump is airlocked (see images of a check valve and a recirc. Pump below).

Sorry to say the plumber's excuse is nonsense. You can have hot and cold water pipes touching all day long... won't cause issues when hot water is called for... *UGH*.

Back to you...

Mark

Thanks for the quick response. I don't see anything like either device you attached. I figure it would be right where the cold water meets the tank but all I see is this (see attached). Pipe comes straight up and into tank but this looks like a simple shut off valve. Where should I look?

As you can see by the image not all pumps are located next to the tank. Regards, Tom

Yeah, see if any of the branches off the hot or cold water supply have a pump or check valve... need to spend time looking/investigating each pipe. Looking under each sink for devices like Tom posted may also allow you to isolate the issue to a specific area/device/part... ;)

Good luck!

Dewds I checked everywhere and I can find no device like the one pictured. Everything seems to appear like normal straight through pipes to the faucets. We do have a pretty crazy config where the pipes branch off to the radiant floors, sink, and dishwasher. Aside from that I don't see anything odd.

You say, "We do have a pretty crazy config where the pipes branch off to the radiant floors, sink, and dishwasher"...

What does that mean... radiant floor heat should not be connected to your hot water heater in any way at all unless you have a completely separate water heater just for the radiant floor heat, otherwise, there should be no connection between domestic hot water and heat?

This could certainly be part or all of your issue... maybe? Please clarify or post a picture, OK?

Mark

Don't take my word I am just trying to guess at what is going on (see attached). Black hose dumps water from the clothes washer, pipes marked with red seem to go to/from the slab, green is sink drain and dishwasher drain, and copper pipes seem to bring water to the sink. This is under the kitchen sink BTW. From the right of the sink in the plumbing circuit is only the washer and then the water tank. To the floor feeds, I'm guessing, the rest of the house and the radiant floor network. Don't really know what else to say... maybe you guys want to come take a look LOL ;)

Mark or Tom maybe you are still around to see this. I found the sucker. A grundfos 1542 F off the gas furnace. I didn't think to check but as the temp dropped and I began to fiddle with the burner to get the heat going I saw the UP circulator. Could this be causing me grief at the burner? It is right after the outlet from the furnace... Or if anyone else has light to shed please do so. :)

Hi TD

That could be a recirc. Pump and that would definitely be the issue, but be careful here... could also be the circulator for your heat loop... ;)


Look at the system and see if you can separate the heat from the water. If you can, you should be able to decide if this is a domestic water circulator or a heat system circulator, OK?

Let us know more and then we can tell you the "next step".

Mark

Quote:

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Originally Posted by massplumber2008

Hi TD

That could be a recirc. pump and that would definitely be the issue, but be careful here...could also be the circulator for your heat loop...;)


Look at the system and see if you can separate the heat from the water. If you can, you should be able to decide if this is a domestic water circulator or a heat system circulator, OK?

Let us know more and then we can tell you the "next step".

Mark

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Unfortunately it's the heat system because it's setup right before delivery of water to the radiant flooring. So that's not the problem I guess? What do you think?

If you're up for it I want you to try a different approach on this... ;)

Here, I want you to shut off all the HOT water shutoffs under all the sinks with SINGLE HANDLE faucets only. Also shut off the hot water supply to the washing machine. Now, try running the showers and see if you have hot water quickly. If you do I want you to open one shutoff under a sink at a time and check the temperature at the shower(s) each time... see if there is a change in temp. after you open each one. If you find a temp. change then I suspect that you have a bad MIXING CARTRIDGE at a faucet and that mixing cartridge will need to be replaced. If you find the temp. changes when you open the washing machine hot supply then you have to figure that the solonoid valve at the washing machine is bad and needs to be replaced.

One thing that adds to the difficulty here is that shower valves are single handle and can not usually be isolated so you can shut off the hot supply to do this test. Here, if you can find no source of CROSS CONNECTION (that's what we are looking for here...a place where hot and cold are mixing when they shouldn't) then one of the shower valve mixing cartridges could actually be the culprit and in that case those mixing valve cartridges need to be replaced. In cases like this, after I have exhausted all other avenues, i.e. eliminated all other sources of cross connection as the issue, I usually replace the shower valve cartridges and that has almost always resolved the issue!

Start by isolating as many valves or cross connections as you can find in your house and then work your way backward while testing at the shower valves (as mentioned)... see what happens.

If any of the shutoff valves leak behind the handles of the shutoffs, just righten the PACKING NUT (behind the handle) a bit to stop the leak.

Let us know what you discover, OK?

Mark