Hot Water Coming Out Cold Water Throughout House??

[aumfc]

Built a new house and moved in April last year. Since we moved in, when we turn on the cold water only anywhere in the house, we get warm to very hot water for anywhere from 20 seconds to 3 or 4 minutes, depending on where we are in the house and time of day. The house is 6,000 sf and one level, with 20+ cold water drops. This happens on the other side of this wall, all the way to the other side of the house, including the outside hose bibs and refrigerator water lines.

The builder and plumbers have been out multiple times and can't seem to fix it. They haven't been out in a while, saying they are trying to figure it out but I don't have much hope. If the recirc pump is off, this doesn't happen. However, when it's off, our master bathroom and shower, which is furthest from the heaters, never really get hot and take a while to even get warm.

We are on well water with 2 hot water heaters and a recirculation pump (F in photo). The line from the well filtration units runs ~125' to the hot water heaters (C). The heaters are in the SW corner of the house in the garage. Hot water runs from there to the far end of the house through probably a good 150' of pex. At the end of the hot water line run, a dedicated recirculation line takes it back to the heaters (B). (A) in the photo goes to a hose bib, which is turned off right now.

The plumbers have tried adding check valves, (D) and (E), but it didn't solve the problem.

Any ideas? I don't know what else to try and the professionals haven't been any help over the last 9 months.

Thanks.

 

[WorthFlorida]

You have to eliminate and then isolate. Have you turned off the pump and closed valves to eliminate the circulation system?

Shut off all valves to all water fixtures including the washer. DW can be left alone. Shower valves if possible.
One at a time open the cold valves at one fixture, run the cold water And see if it's hot. If not open the hot valve and run the water.

Do you have a touchless kitchen faucet? Bath and shower valves can cause a cross over. The tempering valve might be stuck allowing hot water to cross over to the cold.

What is unusual is the cold is hot at first. Cold water lines always have higher pressure than hot water lines. Cold water will mix with the hot and push out warm water at a water fixture.

 

[Sponsor]

 

[aumfc]

You have to eliminate and then isolate. Have you turned off the pump and closed valves to eliminate the circulation system?

Shut off all valves to all water fixtures including the washer. DW can be left alone. Shower valves if possible.
pOne at a time open the cold valves at one fixture, run the cold water And see if it's hot. If not open the hot valve and run the water.

Do you have a touchless kitchen faucet? Bath and shower valves can cause a cross over. The tempering valve might be stuck allowing hot water to cross over to the cold.

What is unusual is the cold is hot at first. Cold water lines always have higher pressure than hot water lines. Cold water will mix with the hot and push out warm water at a water fixture.

We know that turning off the pump fixes it.

The plumbers spent many hours turning valves on and off and could never figure it out. A complicating issue is that due to the amount of water, sometimes it may start not-cold, get warmer after 20 seconds, stay warm a couple minutes, then go cold.

If you do that at one sink, then immediately go to the next sink, it may start cold immediately. But if you started at the second sink, you'd have the same problem in reverse. There are 65 total drops, I want to say. After a couple of tests, all the sinks will seem to run cold out of the cold for a period of time until the problem starts again.

Yes, we have a couple of touchless faucets and 6 bath/shower valves. They all seem to work normally, outside of the main issue. How can I test if there is a valve issue?

 

[John Gayewski]

Just to be sure the check valve on D and E have the arrows pointing toward the water heater?

 

[aumfc]

Just to be sure the check valve on D and E have the arrows pointing toward the water heater?

It's very difficult to see. They are made by different manufacturers. E looks to have a small arrow pointing towards the heaters and the words are oriented in the direction of the arrow. I couldn't locate an arrow on D, but its words are oriented towards the heaters like E. Meaning, if it were sitting upright so you could read the words, the heater would be at the top.

 

[John Gayewski]

When no water is being used, but the pump is running does the hot water supply piping get hot along with the recirculation line?

 

[WorthFlorida]

I don't trust touchless because the faucet is open on both sides with a valve to turn off leaving a possibility a cross over.
Tub/showers valve bodies can have stops built in. Some do, some do not. You need to take the cover plate off to access them.
Is pipe B the cold water feed?

A wild ass guess. If all of the PEX is clear, possibly there is a mix up. The cold pipe might be on the hot or return line etc. With that many drops one could be connected to the wrong pipe.

Are the faucets connected via daisy chained or dedicated runs to each fixture? It does look like daisy chain?

 

[JohnCT]

A wild ass guess. If all of the PEX is clear, possibly there is a mix up. The cold pipe might be on the hot or return line etc. With that many drops one could be connected to the wrong pipe.

Since it apparently never worked right, that's what I was thinking.

Off tangent, but the thought of using recirculation on a PEX system worries me. If it was my house, I'd go with home runs of 1/2" hot pipe to each fixture (at least the distant ones) and put up with 20 seconds of wait time.

John

 

[aumfc]

When no water is being used, but the pump is running does the hot water supply piping get hot along with the recirculation line?

Yes. The line leaving the tanks and the link coming back in are warm.

 

[aumfc]

I don't trust touchless because the faucet is open on both sides with a valve to turn off leaving a possibility a cross over.
Tub/showers valve bodies can have stops built in. Some do, some do not. You need to take the cover plate off to access them.
Is pipe B the cold water feed?

A wild ass guess. If all of the PEX is clear, possibly there is a mix up. The cold pipe might be on the hot or return line etc. With that many drops one could be connected to the wrong pipe.

Are the faucets connected via daisy chained or dedicated runs to each fixture? It does look like daisy chain?

Pipe C is the water coming into the house from the well. Pipe B is the recirculation return pipe.

It's not all clear. The cold is blue and the hot is red. There are some clear pieces here and there.

There is a main hot line and a main cold line running the length of the house. Each drop splits off the main line.

 

[John Gayewski]

Yes. The line leaving the tanks and the link coming back in are warm.

The line leaving the tank should be the same temp as the tank, the line coming back should be 20 degrees or less cooler. You said warm but they should be pretty hot.

 

[John Gayewski]

I never set up recirculation lines like they have it. First of all you should only need one check valve with the pump on the return side shooting into the bottom of the tank. Second with the tanks in series it's hard to tell what's happening since you can't isolate anything from one another.

 

[aumfc]

The line leaving the tank should be the same temp as the tank, the line coming back should be 20 degrees or less cooler. You said warm but they should be pretty hot.

I don't know exactly how warm the lines are. I'll check to see.

 

[aumfc]

I never set up recirculation lines like they have it. First of all you should only need one check valve with the pump on the return side shooting into the bottom of the tank. Second with the tanks in series it's hard to tell what's happening since you can't isolate anything from one another.

The check valves have been added in attempts to fix the problem.

You're saying the pump needs to be connected to the line going directly into the first tank, instead of the line coming directly out of the second tank?

 

[Fitter30]

Are there valves on the hot lines before the all the faucets? If not they have to put them in if not can't find which device has the cross connect.

 

[Bgard]

First you need to find a new plumber! The pump MUST be on the return line, connected to where the boiler drains are at the bottom of the two tanks, via a balanced tee arrangement ( a tee with the bull exactly the same length from each connection point at the tank), the cold water supply MUST be connected to the cold water inlet at both water heaters, and the hot supply out MUST be connected to both heaters in the same manner, ( balanced tee ). There is another method of plumbing called First in Last out which would be good to use on the cold in and hot out of the heaters but the balanced tee system will work IF the lengths out of the run of the tee’s is exactly the same including any fittings. You could then put a aqua stat on the common return to the heaters that would turn the circulating pump off when the water is at the set point, otherwise the return loop becomes a radiant heat loop constantly giving up heat.

 

[John Gayewski]

First you need to find a new plumber! The pump MUST be on the return line, connected to where the boiler drains are at the bottom of the two tanks, via a balanced tee arrangement ( a tee with the bull exactly the same length from each connection point at the tank), the cold water supply MUST be connected to the cold water inlet at both water heaters, and the hot supply out MUST be connected to both heaters in the same manner, ( balanced tee ). There is another method of plumbing called First in Last out which would be good to use on the cold in and hot out of the heaters but the balanced tee system will work IF the lengths out of the run of the tee’s is exactly the same including any fittings. You could then put a aqua stat on the common return to the heaters that would turn the circulating pump off when the water is at the set point, otherwise the return loop becomes a radiant heat loop constantly giving up heat.

I agree that the piping isn't what I would do, but the way it's piped is a common way to do it. They could change everything just the way you describe, but if the problem is a cross connection the problem wouldn't resolve.

 

[John Gayewski]

You're saying the pump needs to be connected to the line going directly into the first tank, instead of the line coming directly out of the second tank?

No. The style of recirculation they are using here is called injection. Where they inject the return water into the tanks through the cold water supply piping using check valves to direct it. Vs the way I prefer to do it which is more elegant in my opinion.

I would like to know the supply water temp and the temp of the return line. I would also like you to confirm the check valves are pointed the right way. You should be able to use a mirror or a phone camera to see every angle and find the arrows.

The fact that they added the check valves after means they didn't know they needed them, which makes me think they don't know what they are doing.

The thing that's throwing me off is your statement that turning off the recirculation line fixes the problem. This must mean you have mixing valves at some or one of your faucets or your have electronic faucets.

 

[Bannerman]

A check valve will be need on the Cold inlet connection of each touchless faucet.

To easily verify hot water is flowing in reverse into the cold supply lines through the touchless faucets, while the recirculation pump continues to be active, feel the temperature of the cold supply line to each touchless faucet after no water has been drawn from that faucet for some time (ie: > 30-minutes). When no cold water has been drawn for 30-minutes or longer, the cold water line will usually have warmed up close to room temperature, but hot water passing through the faucet into the cold line, will cause the cold supply line to be hot, virtually equal to the temperature of the hot supply line.

 

[GReynolds929]

That pump is from a home comfort recirculation system. It uses a Thermostatic bridge valve to return the hot water to the tank via the cold water line. Usually used in houses with no dedicated recirc system. Under one or more of your sinks there will probably be a brown tee like device. Having a dedicated return is definitely odd if there are bridges used. As stated above touchless faucets are a prime suspect otherwise.