Questions about Recirculating Pump vs Water Softener

[takedownca]

Hello. I'm a new homeowner and am planning to install a timed or flow sensor-triggered recirculating pump at my water heater as well as sensor bypass valves under my kitchen and bathroom sinks. But I have lots of questions/concerns about how this will affect my water softener.

I’ve attached a simple layout that I believe represents what my plumbing would look like with the pump installed. Hopefully it helps clarify my convoluted ramblings.

1. When I moved in, the builder told me that the kitchen water is not softened. However, I see only one pair of in/out at the water heater. Am I right in assuming that only the cold kitchen water is hard, but the hot kitchen water is soft?
   
   
2. If I put a sensor valve under the kitchen sink, am I now sending hot soft water back through the softener? Is that a problem for my water softener, or am I just going to run through softener salt a little faster?
   
   
3. I could be wrong, but I don't believe there is a check valve after the water softener. Does that mean hot soft water will circulate backwards through the softener or somehow hamper the venturi flow? Is a check valve necessary?

Little background; I have a Rinnai V75 tankless water heater and a softener using a Pentair 5810 valve. The recirc pump is a generic sensor-driven pump with max 20ft head. I've attached pictures in case it helps.

Thanks for any insight. I’m just trying to avoid making any unplanned plumbing mistakes.

 

[Reach4]

You have correctly anticipated a real problem. Good going. If you want hot water recirculation at the kitchen, you will need to run a separate recirc line, or you will need to re-route the kitchen cold faucet to use softened water.

I don't know how recirc is going to do with your tankless. Some have provision for that, and maybe yours does. Recirc may not be for you. In San Diego (expensive water, expensive electric, mild temperatures), maybe you should tough it out and wash your hands with room-temperature water in the kitchen, or go to a lavatory to wash your hands.

 

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[takedownca]

@Reach4, thanks for the quick reply! I feared as much. I'd like kitchen recirc, but it's not worth excavating my walls to install a separate return line. I'm not too worried about washing my hands with cold water, but my wife and baby don't much appreciate the cold hands afterward The main reason for wanting recirc for the kitchen is for the dishwasher. At the moment I'm getting a white glaze on all my glasses, and I suspect it's because it takes so long to get hot water that the soap doesn't properly dissolve. To battle this I've been running the hot water before I run the dishwasher, but this defeats the water savings of having a dishwasher. I wish the builder had a recirculation option when I was spec'ing the house Maybe I'll get lucky. If the kitchen line isn't too long a branch, the bathroom recirc will speed up the kitchen hot water a bit by circulating the main trunk line ¯\_(ツ)_/¯ I also now have an extra sensor valve, but I hear they fail often enough. So it doesn't hurt to have a spare around.

I think the tankless should be fine. I believe the recirc pump generates enough pressure to get the heater started. And as long as I'm running the pump only intermittently, it won't void the warranty.

Last question. What about the check valve? Is there a risk of softener malfunction due to back flow, or should my softener valve be able to handle it? I looked at the 5810 manual and didn't see anything about having a built-in check valve or unidirectional flow. In theory the tankless should have lower back pressure and be an easier flow path, especially with the recirc pump sucking water through the hot line. But I'm no expert. I can also put the pump on a timer so it doesn't run when the softener is scheduled to run.

 

[Reach4]

The main reason for wanting recirc for the kitchen is for the dishwasher. At the moment I'm getting a white glaze on all my glasses, and I suspect it's because it takes so long to get hot water that the soap doesn't properly dissolve.

I suspect it is TDS on the glasses. Since you have a softener, that will be mostly sodium compounds if that is the case. Those rinse off. Maybe use more Jet-Dry.

You could try running a cycle with no soap, or you could try liquid dishwasher soap. Those Cascade packets are handy and powerful, however.

Last question. What about the check valve? Is there a risk of softener malfunction due to back flow, or should my softener valve be able to handle it?

You would not damage the softener. While backflow would not damage the softener either, this would be forward flow. The only downside is that the softener will detect that as water being softened, so will schedule a regeneration a little earlier. One thing is that you could use the softener diagnostics to measure that flow if you were so inclined.

You may be interested to know that some people have had their softeners plumbed backwards for years, and don't notice an effect.

Maybe I'll get lucky. If the kitchen line isn't too long a branch, the bathroom recirc will speed up the kitchen hot water a bit by circulating the main trunk line ¯\_(ツ)_/¯

Yes. You say sensor driven. So you may be running a little hot at the bathroom before doing dishes. Most efficient would be button-triggered rather than motion sensor or flow sensor.

How about changing the piping to the kitchen to use softened water? If you put in a reverse osmosis unit, those should be fed with softened water anyway. If you put in RO, make sure any water line to the fridge is plastic rather than copper.

There are people who are good at fishing coax and ethernet cables through walls. Maybe one could get you a return path with PEX through some walls and the attic

 

[takedownca]

Those Cascade packets are handy and powerful, however.

Yep, I use the packets with built-in rinse agent. Unfortunately, my glasses are still foggy. I guess I could try liquid soap and/or extra rinse agent.

While backflow would not damage the softener either, this would be forward flow.

Good to know, but I'm a little confused. Wouldn't the check valve be for avoiding back flow (not fwd flow) resulting from bathroom recirculation? And the kitchen recirc would be a source of source of fwd flow... at least according to my diagram? But if forward flow is fine, then what is wrong with installing a bypass at the kitchen? I would just end up with a faster recharge schedule and some soft water in my hard water line, right? Or is the problem overcoming the high back pressure coming from the city? People don't give plumbers enough credit for taking all this stuff into account!

Most efficient would be button-triggered rather than motion sensor or flow sensor.

Curious - why is that? This pump is supposed to sense when you briefly use hot water. After that, it will keep pumping until the sensor valves shut off at about 95deg. That more or less works the same as a push-button, right? I can also plug the pump into a smart outlet and directly control or schedule it.

There are people who are good at fishing coax and ethernet cables through walls. Maybe one could get you a return path with PEX through some walls and the attic

That's a thought. Maybe later. Hiring someone would double or triple the budget I have for this particular project. Also, the kitchen sink is in an island, so the return line would be going through slab. Don't think that can be fished :/

 

[Reach4]

Good to know, but I'm a little confused. Wouldn't the check valve be for avoiding back flow (not fwd flow) resulting from bathroom recirculation? And the kitchen recirc would be a source of source of fwd flow... at least according to my diagram? But if forward flow is fine, then what is wrong with installing a bypass at the kitchen? I would just end up with a faster recharge schedule and some soft water in my hard water line, right? Or is the problem overcoming the high back pressure coming from the city? People don't give plumbers enough credit for taking all this stuff into account!

The bathroom cold is from after the softener. Therefore that recirc does not send water through the softener.

Yes, recirc into the cold for the kitchen does no harm other than the softener regenerating a little early maybe, and also turning your cold faucet into warmer softened water at times. I drink softened water, but the motivation for running unsoftened water to the kitchen in the first place is that some people want fill their drinking glass with unsoftened water.

Curious - why is that? This pump is supposed to sense when you briefly use hot water. After that, it will keep pumping until the sensor valves shut off at about 95deg. That more or less works the same as a push-button, right? I can also plug the pump into a smart outlet and directly control or schedule it.

If it senses the use, it will still take time for the WH to start and hot water to arrive. So I guess you run and maybe discard a bit of water, turn the faucet off, and then wait. If you could just push a button, you would not waste any water just to trip the sensor. Some use a motion sensor, but that waste electricity. And that SD electricity is really good stuff, because we know you get what you pay for. ;-) Just joking of course. A minute or two of pumping is nothing in KWH.

 

[WorthFlorida]

Most dishwashers heat the water during the wash cycle unless you have an energy saving wash that may not turn on the heater. With a water softener and very strong detergent it will etch the glasses and it is probably what happened here.

With a softener you only need to use about a 1/3 or less soap if you ever used the powder and fill up the depensor cup. A full cascade packet is a lot. Try hand washing the glasses with soft scrub and you’ll may find the cloudiness doesn’t go away.

 

[takedownca]

The bathroom cold is from after the softener. Therefore that recirc does not send water through the softener.

Ok, sounds good. Seems like I don't need to install a check valve. One less thing to do!

So I guess you run and maybe discard a bit of water, turn the faucet off, and then wait. If you could just push a button, you would not waste any water just to trip the sensor.

We'll see what works best. Either flow or button trigger would work for me. In the end it's whatever I can actually get my wife to do. I don't see her pushing a button every time she wants to wash her hands, but a quick turn of the faucet seems more feasible for her. Even if she doesn't wait, the pump + bypass valves will make the water hot faster. And yes, that SD electricity is quote good. If cost is any indicator, it's getting better every year!

I drink softened water, but the motivation for running unsoftened water to the kitchen in the first place is that some people want fill their drinking glass with unsoftened water.

If anyone wants room temp drinking water, I have a filter under the sink and a separate dispenser. It may or may not filter sodium, but nobody in my house has blood pressure problems, so I think I'm good to go.

Looks like I'll be proceeding as planned with a bypass under each sink including the kitchen. But thanks for helping me hash things out. I didn't want to inadvertently break my softener or worse!

 

[takedownca]

Most dishwashers heat the water during the wash cycle unless you have an energy saving wash that may not turn on the heater. With a water softener and very strong detergent it will etch the glasses and it is probably what happened here.

With a softener you only need to use about a 1/3 or less soap if you ever used the powder and fill up the depensor cup. A full cascade packet is a lot. Try hand washing the glasses with soft scrub and you’ll may find the cloudiness doesn’t go away.

I haven't looked too closely, but it seems like I can get the cloudiness out by scrubbing or even scratching hard with my fingernail. I just don't have any desire to scrub and wash my glasses again after I take them out of the dishwasher. Go figure.

I'll take a closer look to see if the stain is actually removable. If not, I'll have to try moving from packets to a smaller amount of liquid or powder soap. Ironically, I've been trying to use hotter cycles because I thought the problem was soap not dissolving. If what you're saying is true, doing that might have actually caused more etching.

It doesn't make sense, though. What about the soap, softened water, and high temperature is going to etch glass? The soap should never etch glass regardless of temperature. Softened water has less mineral deposits but a tiny bit more sodium. Since when does sodium etch glass?

 

[WorthFlorida]

It’s not the soften water itself, its what it does with detergents. Ion sodium water is extremely water soluble and dishwashing detergents generally have very high ph levels.

https://www.hunker.com/12304434/how-to-prevent-glass-etching-in-the-dishwasher

https://www.hunker.com/13423926/how-to-remove-etching-from-glass

https://www.consumer.org.nz/articles/dishwasher-detergent-safety

 

[Jadnashua]

If you DW has a sensor preheat, turn it on. IF it doesn't, when you replace the DW, consider buying one that has that feature as an option. Any of the DW work better if the water is hotter, but liquid detergents may leave fewer deposits if yours isn't within the suggested range. If the water is hot, either should work fine.

 

[WorthFlorida]

From https://www.hunker.com/13423926/how-to-remove-etching-from-glass

Detergent Details


Dishwasher detergents sometimes use harsh chemicals called phosphates to get the job done, and these chemicals can etch glass. Soft water gives the cleaning agents a boost and helps them perform better, but this boost is potentially too much for glass. The softer your water, the less detergent you need. If your glassware leaves your dishwasher etched, it's time to get rid of the popular pre-measured detergent pods and go back to filling the detergent cup manually. Have your water tested for hardness and then use the recommended amount of detergent for your results:

• 0-3 Grains Hardness: Use 1 tablespoon of detergent (fill dispenser cup 1/4 full)
• 4-6 Grains Hardness: Use 2 tablespoons of detergent (fill dispenser cup 1/2 full)
• 7-9 Grains Hardness: Use 3 tablespoons of detergent (fill dispenser cup 3/4 full)
• 10-12 Grains Hardness: Use 4 tablespoons of detergent (fill dispenser cup completely full)

 

[takedownca]

Thanks guys. Not sure which knob to tweak - water temp, detergent type, detergent quantity, etc - but I’ll try fiddling with them all.

 

[Reach4]

Here is what I would suggest you try for diagnosis: take one of the glasses, that gets spots, from the dishwasher after final rinse, but before much time in the drying. Rinse under the softened hot faucet. Shake off the water, and spray the glass generously with distilled water. Shake off the excess, and let the glass air dry. No wiping.

Spots?