Watts Hot Water Recirculating System

[Mitchell-DIY-Guy]

In the retirement community I often work in (repairing shelving today, fixing doorbells, changing out smoke detectors) one of my clients, then tells me that there seems to be an issue with their Watts Hot Water Recirculating System. This is the Watts 500800 pump which is at the water heater in the garage, and the 596816 sensor valve kit which is under the kitchen sink. They tell me there's hot water at both hot and cold taps now.

Cross connection. Am I right in my guess that this bypass valve assembly needs to be replaced? The other possible scenarios would indicate that the pump is running all the time or too frequently, and as the home is 10 years old and this is their first problem with it...I don't think anyone's messed with the pump.

 

[MicEd69]

Am I right in my guess that this bypass valve assembly needs to be replaced?

Yes. The sensor valve is supposed to open only to allow relatively cool water back into the cold-water supply line to the faucet. It appears to have failed and is allowing "hot water" into the cold-water supply line. They will then have "hot water" coming out of the cold-water faucet until that "hot water" is purged out of the cold-water supply line.

 

[havasu]

Anyone know if the sensors are available at the big box stores, or do they need to be ordered?

 

[havasu]

Wouldn't it be feasible to disconnect the sensor to confirm the cross over is not coming from another valve? Seems like an easy verification?

 

[MicEd69]

Anyone know if the sensors are available at the big box stores, or do they need to be ordered?

Menards has them near me, but the Home Depot near me needs to order them. I can get them overnight from Amazon as well.

 

[Twowaxhack]

I believe the sensor valve closes at 95 degreees.

So you might have 95 degree water at the cold tap for a few seconds.

 

[Mitchell-DIY-Guy]

I believe the sensor valve closes at 95 degreees.

So you might have 95 degree water at the cold tap for a few seconds.

So let me see if I understand how these work:

1. If the temperature of the water in the HOT WATER line at the fixture where that valve is located is below 95 degrees (or so), the valve is OPEN.
2. If the pump's timer is set to on (say in the morning or evening or whatever the set point is) it starts pumping hot water (circulating) and the hot water has a return path through the open valve and cold water lines back to the hot water heater.
3. When the valve's fixed set point is achieved (above 95 degrees or so) it closes, no circulation is possible, and none is needed: you already have hot water at the fixture.
4. The pump has a built in timer, so you set a few brief "on" periods during the day. When the pump is "off" there is no circulation and you wait for hot water as usual.

Do I have that about right? If not, someone correct me, please.

I would think however, that say you have the pump timer set to 5 pm to turn on, and the valve is under your kitchen sink. You have this set so when you start dinner, you don't wait for hot water. However, as that valve is open and the pump is running in order to quickly get hot water to the fixture, BOTH hot and cold lines to the kitchen sink are now full of hot water. If you want COLD water you are going to wait nearly as long for the water to get cold, as you would have to get it hot in the first place.

If I have this even close to correct it seems you are trading waiting for hot, for waiting for cold when the pump is running?

 

[Twowaxhack]

The valve isn’t open so to say or that would cause a cross connection. The pump must be on for the valve to be “ open “ and temp must also be below 95 degeees. The pump must run to allow crossover. This keeps a cross connection from happening when the hot water side is below 95 and the pump is OFF.

Not much cold water (warm) would need to be purged.

But yes, it puts warm water into your cold line at the crossover valve.

 

[MicEd69]

Yes, pretty much. And that is why a dedicated water return line is MUCH better. That way, you have actual "hot" water near each faucet and actual "cold" water at each faucet.

 

[Twowaxhack]

Yes, pretty much. And that is why a dedicated water return line is MUCH better. That way, you have actual "hot" water near each faucet and actual "cold" water at each faucet.

It depends on the users needs and expectations. Some people just want warm water to wash their hands with and the bypass with pump is much more economical to install. It’s also a little more economical to operate as you’re not circulating full temp water that may not be needed.

 

[Mitchell-DIY-Guy]

My client had hired a plumber to "fix" the problem of hot water in the cold line, probably caused by the valve(s) (there are two of them, one in kitchen and one in remote bathroom in a ranch house). I guess the plumber wasn't at all familiar with these or testing them. Played around with it for a while and gave up. She (lady plumber) then actually just removed the valves! So no way it works now.
It looks easy enough to install, and it DID work for them for many years. So, I suspect one or more of those valves are bad.

 

[MicEd69]

It depends on the users needs and expectations. Some people just want warm water to wash their hands with and the bypass with pump is much more economical to install.

Yep.

It’s also a little more economical to operate as you’re not circulating full temp water that may not be needed.

Except if you are manually operating the pump and only turn it on when you actually need hot water in the next 4-5 minutes like I do.

 

[Twowaxhack]

Yep.


Except if you are manually operating the pump and only turn it on when you actually need hot water in the next 4-5 minutes like I do.

I’ve only met one person that does that. Most people I’ve worked for don’t want the inconvenience of manually starting a hot water pump is what I find. A motion sensor would do the job but most just want a timer with morning and night set times OR run it all the time.

It’s a personal choice. I just lay out the options.

 

[Twowaxhack]

I just installed one of the watts pumps with the bypass valve.

The customer purchased it and requested I install it.
His master bath has approximately 80’ of 3/4” pipe between his 50 gal electric heater and his master bath.

He doesn’t like that the water isn’t HOT. I explained it wouldn’t be full temp before I installed it.

He wants options now.

I gave him the option of installing a dedicated return or installing another water heater closer to the demand.

My recommendation was to install a small tankless natural gas water heater on the exterior wall right outside the master bath. For his size house he needs more hot water than a 50 can supply and the tankless would provide almost instant and unlimited hot water with zero standby loss.

My guess is he won’t do anything but live with what he has.

 

[MicEd69]

I’ve only met one person that does that. Most people I’ve worked for don’t want the inconvenience of manually starting a hot water pump is what I find. A motion sensor would do the job but most just want a timer with morning and night set times OR run it all the time.

It’s a personal choice. I just lay out the options.

Yeah, in today's instant society, everything has to be instant.

But all I have to do is push a button, brush my teeth, then immediately turn on the shower for hot water.

And my wife pushes a button, collects the dirty dishes in the sink, then turns on the hot water to wash the dishes she needs to hand wash.

Easy with minimal wasted energy in pumping hot water when it is not needed.

 

[Twowaxhack]

Yeah, in today's instant society, everything has to be instant.

But all I have to do is push a button, brush my teeth, then immediately turn on the shower for hot water.

And my wife pushes a button, collects the dirty dishes in the sink, then turns on the hot water to wash the dishes she needs to hand wash.

Easy with minimal wasted energy in pumping hot water when it is not needed.

You wouldn’t rather have a motion detector in the bathroom ?

 

[wpns]

I turn on the shower, brush my teeth, and then the shower’s hot. 2 gallons per minute, 2 minutes, ‘wasted’ 4 gallons of water. . Zero install cost, zero maintenance

 

[MicEd69]

You wouldn’t rather have a motion detector in the bathroom ?

No, I don't always take a shower when I enter the bathroom. Why would I want to turn on the hot water circulating pump every time my wife or I went into the bathroom? She's always in there brushing her hair, brushing her teeth, putting on makeup, etc.

 

[Twowaxhack]

No, I don't always take a shower when I enter the bathroom. Why would I want to turn on the hot water circulating pump every time my wife or I went into the bathroom? She's always in there brushing her hair, brushing her teeth, putting on makeup, etc.

I rinse my toothbrush with hot water when I’m finished with it and I wash my hands after I use the toilet and I use warm water to so.

So that basically means whenever I’m in my bathroom that I’m probably going to use some hot water.

 

[Twowaxhack]

You could always install a motion detector and wire in a delay on break to the pump so once it activated once that it has a set time to sit idle before it’s started again.

Sequence of operation :

Motion detected, pump turns on, pump turns off, delay starts (30 min, 60 min ) etc, pump resets.

This way your wife wouldn’t be restarting the pump the whole time she’s in the bath. You could set the delay to any time period you wanted.

Look, I’m trying to give you some work to do. So get busy and post the pictures as you tear into it.

I’m about to load up my equipment and head out to a backed up sewer with water coming out from under one toilet and holding water in the tubs and other toilet. No cleanout. Too bad you’re not around here, I’d come pick you up.