Watts Recirculation Pump and Water Hammer issue

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Drip

Member
Joined
Mar 17, 2024
Messages
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Location
Under the sink
I have had a Watts 500800 recirculation pump installed for a few years without issue. The pump is on the water heater in the garage and the sensor valve is installed at the kitchen faucet about 40 feet away on the first floor. Within the last 6 months or so, I have noticed a water hammer effect when turning off the hot water at the kitchen sink. The sound appears to be coming from an outside wall in the general vicinity of the kitchen but I haven't been able to pinpoint the exact location yet. It appears that this only happens when the recirculation pump is running. It will hammer for 3 or 4 subsequent shutoffs but then it will stop for a while then return.

As far as I know, the water lines go from the water heater in the garage, through the adjacent wall to the laundry room, then they go under the slab to the kitchen. How can it be that I am hearing the hammer in a wall? The hammer sound isn't coming from the recirc pump/water heater area. I talked to Watts about this and they recommend removing the tiny check valve from the sensor valve. I have done this and the problem persists. I have also installed small piston style T-type water hammer arrestors rated for 350 psi on both the hot and cold lines at the kitchen faucet and the problem persists. I have checked the water pressure coming into the house. While I have occasionally seen high numbers, for the most part, the pressure hovers right around 70 psi, so I have generally ruled out the pressure regulator. At this point, I am completely stumped. I have not tried replacing either of the water hammer arrestors to see if they are defective. I am unaware of any way to actually test a water hammer arrestor without simply replacing it. Would it make sense to install a hammer arrestor by the recirc pump/water heater?

Any ideas/thoughts/suggestions would be appreciated.
 
Drip said:
I have had a Watts 500800 recirculation pump installed for a few years without issue. The pump is on the water heater in the garage and the sensor valve is installed at the kitchen faucet about 40 feet away on the first floor. Within the last 6 months or so, I have noticed a water hammer effect when turning off the hot water at the kitchen sink. The sound appears to be coming from an outside wall in the general vicinity of the kitchen but I haven't been able to pinpoint the exact location yet. It appears that this only happens when the recirculation pump is running. It will hammer for 3 or 4 subsequent shutoffs but then it will stop for a while then return.

As far as I know, the water lines go from the water heater in the garage, through the adjacent wall to the laundry room, then they go under the slab to the kitchen. How can it be that I am hearing the hammer in a wall? The hammer sound isn't coming from the recirc pump/water heater area. I talked to Watts about this and they recommend removing the tiny check valve from the sensor valve. I have done this and the problem persists. I have also installed small piston style T-type water hammer arrestors rated for 350 psi on both the hot and cold lines at the kitchen faucet and the problem persists. I have checked the water pressure coming into the house. While I have occasionally seen high numbers, for the most part, the pressure hovers right around 70 psi, so I have generally ruled out the pressure regulator. At this point, I am completely stumped. I have not tried replacing either of the water hammer arrestors to see if they are defective. I am unaware of any way to actually test a water hammer arrestor without simply replacing it. Would it make sense to install a hammer arrestor by the recirc pump/water heater?

Any ideas/thoughts/suggestions would be appreciated.
Click to expand...
Turn the Circ pump off and then see if it still hammers at the kitchen valve.
 
Thanks for your interest.

It's a single speed pump, it's either on or it's off. It operates on a timer. I have it set to run at peak usage times during the day.

Here are some pics:

Pump.jpg

Arrestors.jpg

It just occurred to me. Maybe the arrestors should attach to the sensor valve instead of the on/off valves as they are now. Would that make a difference?

What do you think?
 
Drip said:
Thanks for your interest.

It's a single speed pump, it's either on or it's off. It operates on a timer. I have it set to run at peak usage times during the day.

Here are some pics:

View attachment 45026

View attachment 45027

It just occurred to me. Maybe the arrestors should attach to the sensor valve instead of the on/off valves as they are now. Would that make a difference?

What do you think?
Click to expand...
Did they tell you to install the circuit pump on the hot water side?
That type of setup, it's forcing the water to go in a direction it doesn't want to go.
Does the pump turn off when you turn the cold water on?
 
This is from the manual:


Install pump onto the water heater discharge, using the
3/4" female fitting and gasket supplied on the pump. The
pump should be installed so that the pump is pumping
away from the hot water heater, towards the house. Con-
fi rm the direction of pumping by observing the fl ow arrow
on the side of the pump housing.

1713303302878.png
 
I'm almost positive that the hammer only happens when the hot water is running. Since I'm not the only one in the house I can't be totally certain, but I have only observed it with the hot water running.
 
This is exactly how my pump is installed. Luckily, I don;t have any water hammer issues. 20151029_120319_resized.jpg
 
havasu said:
This is exactly how my pump is installed. Luckily, I don;t have any water hammer issues.
Click to expand...

That looks right. I'm guessing most people don't have this issue. It didn't appear for me until after several years of use.

Out of curiosity, is your pump sitting on top of an anode rod?
 
Could it possibly be in the device under the kitchen sink. I've installed many of these and never had pipes hammering
either. Call watts and see if they'll send you a new one. Especially if you done nothing different to cause this all of a sudden
 
I just spoke to a knowledgeable plumber who advised that it sounds like a defective thermostat coupler under the sink.
 
It could be the sensor valve. Apparently they do wear out. I'll get another one and see what happens. Thanks for the input
 
If you're going to start throwing around extremely technical terms like "doohickie", I'm afraid I won't be able to follow the discussion. Can you please try to keep it simple for us amateurs? :p
 
Try replacing that thermo bypass valve "doohichie" then if that doesn't work the shock absorbers that are on the emergency shut off(angle stop valves). Also what is your house pressure? Check at hose bib by the main water coming into the home. Then at water heater when hit water is in use. More then 75 is no good.
 
I just finished an install of this same Watts recirculating pump and sensor valve. I am getting pretty significant water hammer when I turn on cold water on the faucet where the sensor valve is installed. I also only get water hammer when the recirc pump is NOT running. It's a brand new sensor valve so doubting it's faulty? Anyone else have an idea or suggestions for options to address?
 
I'd recommend that you recheck all incoming and outgoing lines from the sensor valve. Also check to confirm that your valves to the faucet are fully opened.
 
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