Thermostatic valve or pressure balance valve?

janesylviaNovember 26, 2012

I am considering Delta 17 series or 17T series shower kit. 17 has pressure balance valve, while 17T has thermostatic valve and I need to buy each item separately because 17T series does not come with handheld shower head.

I know pressure balance valves safeguard against sudden and unexpected temperature shocks while in bath or shower. When a toilet is flushed or dishwasher or other faucets are turned on, it automatically balances hot and cold water pressure. Thermostatic valves allow you to precisely preselect your water temperature beforehand.

Does thermostatic valve also safeguard against sudden temperature shocks if dishwasher is turned on, toilet is flushed, or faucets are turned on? Is it better to choose thermostatic or pressure balance valve for a shower stall? I am living in the San Francisco bay area.

Any input is greatly appreciated.

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mongoct

IN GENERAL:

Thermostatic valves and pressure-balanced valves both provide scald protection.

Pressure-balance valves generally control a temp to +/-3 degrees, thermostatic valves to about +/-1 degree.

PB valves are generally single-control valves. You turn the single lever or knob and essentially get 100% volume flow out of the shower head. How far you rotate the valve selects the water temperature. For the most part there is no true volume or flow control. Each time you turn the valve ON you're getting full flow, rotating the valve simply sets the temperature.

There is a "maximum temperature limit" on PB valves, but in general it's more of a mechanical limit that restricts how far you can rotate the lever versus a true limit on the maximum water temperature that can come out of the valve. You set the water to as hot as you'd like it to be. Then you adjust a set screw built in to the valve. The set screw limits the valve from being rotated beyond that setting. It essentially limits the maximum "hot water" to "cold water" mix ratio coming out of the valve.

If you were to turn up max temp on your water heater, you could get scalding water out of your valve if you don't reset the set screw. If you turn your water heater temp down to conserve resources, you might only get lukewarm water out of the shower head until you reset the set screw.

So don't think of PB valves as controlling the temperature. Think of them as controlling the ratio of hot to cold water that comes out of the shower head. You flush a toilet. The toilet refill now demands cold water. The PB shower valve senses that there is less cold water coming through the supply tubing and in to the shower valve, so in turn it chokes down the amount of hot water coming through the valve to maintain the same hot-to-cold ratio through the valve.

TS valves usually have two controllers. One knob/lever to set the volume flow. Another to control temperature. The two controls allow you to have a trickle flow of water through 100% full flow of water at any temperature, from cold to hot.

You can leave the temp setting in the same place for years at a time and simply use the volume control to turn the water flow on and off.

The scald setting on a thermostatic valve actually limits the actual water temperature to a specific temperature. Turn up your water heater? The TS valve doesn't care. It'll still limit the water temp to the max temp it is currently set to. A TS valve controls the actual water temperature. A PB valve controls the ratio of hot to cold water.

It's a difference that you may or may not ever notice.

In a house with good plumbing, you'll usually not notice a difference between the two valves. They both control the temperature just fine.

If you live in an older house with wonky plumbing where you notice a drop in water pressure out of the shower when flushing a toilet, then a thermostatic valve may be the better choice.

If you want the best temperature control, or if you like to reduce the water flow out of the shower head when shampooing without changing the water temperature, then the thermostatic would be the better choice.

    Bookmark   November 27, 2012 at 2:28PM
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enduring

Mongo, do you mean that the last 2 sentences in your post both suggest getting a thermostatic valve? Or, do you intend to use the new "edit" feature? :)

    Bookmark   November 27, 2012 at 6:50PM
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mongoct

Nope, correct as written.

EDIT: Correct as poorly written.

If you have wonky plumbing, a TS valve would be your better bet.

If you prefer precise temp control, a TS would also be the better choice.

If you're not a slave to shower fashion and you have good plumbing and can accept an occasional temperature shift of a degree or two while showering, and you'd like to get all that for about $100 for the valve and trim kit, then look at the Symmons Temptrol pressure balance valves. They will win awards for durability and reliability. But not for sexy design.

For all the Temptrol valves I've installed over the years, I've only needed replacement parts maybe 2 or 3 times. And that is for valves installed 20 to 30 years ago. Each time Symmons sent me replacement parts free of charge. No questions asked.

That is not a solicitation to try to get you away from Delta. It's a simple statement of my personal experience.

    Bookmark   November 27, 2012 at 7:10PM
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enduring

Mongo, so it sounds like it would be typical for most people to put in the thermostatic valves. Is that right? When would one choose the other a pressure balance valve? It sounds like the thermostatic valves have more features. Is it a cost issue?

    Bookmark   November 27, 2012 at 7:41PM
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GreenDesigns

Most people actually put in pressure balancing valves. Because they are cheap. Not better. Cheaper.

    Bookmark   November 27, 2012 at 7:48PM
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mongoct

It can be a cost issue. Thermostatic can easily be 3 to 4 to 6 times the cost of a pressure balanced when including the trim kit.

Thermostatic valves do provide a higher degree of temperature control and provide a wider blanket of true temperature protection. In general they also offer more control. Temperature and volume versus just temperature.

In typical new construction though, either is fine in terms of performance.

But for sure, Thermostatic valves do, for the most part, have prettier trim kits. The trim kits are more elegant looking. They are available in a wider array of finishes. And the valves are a higher level of technology, so to speak, when compared to pressure balanced valves.

I actually install more thermostatic valves than pressure balanced. And I have to say that when people choose valves, about 90% of the time the initial choice is based on how the trim kit looks. And it's usually a thermostatic that is chosen because their trim kits generally look better.

Some go with that choice because money is not a factor. For others, budget does come in to play, and they might back into a PB valve.

Where budget is a factor, or for people that value practicality over pretty, or for people that have simply requested "inexpensive but bulletproof". My first recommendation is the Temptrol line of PB valves.

The irony is a lot of families will choose a nice pretty and expensive TS for the master bath. Then they will choose a basic inexpensive PB for the kids' bath. Who do you think would actually need the higher level of scald protection? The parents or the kids?

I sometimes see it as style over substance. A Chevy and a Lexus will both get you to work. But one might give a more comfortable ride than the other. On a daily basis both will provide you with decent transportation. But should something go horribly wrong, one car might provide better crash protection than the other, just as one valve can provide better scald protection than the other.

Bad analogy...but does that make sense?

FWIW, I install both types. If I thought one was unsafe or a danger risk, I would not install it.

    Bookmark   November 27, 2012 at 8:18PM
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enduring

Thanks for your thoughtful response Mongo :)

    Bookmark   November 27, 2012 at 8:46PM
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kmcg

I followed mongo's advice and got the Symmons Temptrol for our basement bath. (Thank you!) Under $100, and everyone likes it just fine. For our upstairs bath, I got a Hansgrohe thermostatic, because I really like the idea of being able to keep a static temperature while reducing or increasing volume. Much more expensive than the Symmons, but it sounds good in concept. Not in use yet, so I can't report on a comparison.

    Bookmark   November 27, 2012 at 11:02PM
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enduring

Please do report kmcg, when you get the Hansgrohe in. It is nice to get the report on the Symmons too. Really something to consider.

    Bookmark   November 28, 2012 at 7:06AM
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kirkhall

Do you all have any pictures of the Symmons setup? The ones I find online are not really sufficient... Anyone have it with a tub (like this setup, see link)?

Here is a link that might be useful: Symmons for tub/shower combo

    Bookmark   November 28, 2012 at 2:44PM
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attofarad

I'm wondering about response time of pressure balancing vs. thermostatic. I've only used thermostatic.

It seems that a pressure balancing valve can react almost instantaneously. My experience with Hansgrohe Axor thermostatic is that, when another hot water faucet somewhere turns on, the shower gets colder, then gradually returns to about the same temperature.

Hansgrohe also makes pressure balancing valves with volume controls, or with volume/ diverter, all built together.

    Bookmark   November 28, 2012 at 3:29PM
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attofarad

Another comment about the utility of the thermostatic. My wife likes the shower hotter than I do. Each of us can look at the position before turning the volume control on, and set it to exactly what we like. If we want to make an adjustment, it is very predictable how much the temperature will change for a given rotation of the control.

    Bookmark   November 28, 2012 at 3:36PM
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kmcg

kirkhall - your link is the Symmons setup that I have. It looks exactly like the one in your picture. I can take a photo if you want me to - anything specific you want to see?

    Bookmark   November 28, 2012 at 8:04PM
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kirkhall

KMCG-- I'm hoping to see/understand better the control dials on the trim. And, also, to be honest, how it looks installed with some tile around it... Do you find the center dial "sharp" with the "spikes"?

And, how do you like the function of the head?

    Bookmark   November 28, 2012 at 10:27PM
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mongoct

"Do you find the center dial "sharp" with the "spikes"? "

Though the overall "style" of the trim is the same, they have different versions of trim for the temptrol valve.

There are a couple of versions of the "spikey center dial" that you referred to, several styles of lever handles, etc. Same with the graphics on the temperature ring. Different styles of graphics.

They also sell a different style line that fits the temptrol valve. The Allura comes to mind:

Personally, I prefer lever handles over knobs. Personal opinion. I rotate the lever to point the handle at the same "o'clock" position, it's easy to get your preferred water temp each and every time.

    Bookmark   November 29, 2012 at 10:08AM
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janesylvia

Mongoct, thank you so much for your very detailed information.

Now Delta also has pressure balance valve 17 series which has separate control of water flow and temperature. But as you pointed out, for best temperature control, thermostatic valve is better than the pressure balance valve.

I love the thermostatic valve's feature of "set the temperature and forget it", but I concern how the shower temperature would be affected if someone else turned on faucet and if it's quite uncomfortable. I saw Attofarad brought that up as in his post above:
"It seems that a pressure balancing valve can react almost instantaneously. My experience with Hansgrohe Axor thermostatic is that, when another hot water faucet somewhere turns on, the shower gets colder, then gradually returns to about the same temperature."

I also saw a similar comment on amazon's review on Delta T17T078-SS Leland Tempassure 17T Series Valve Trim Only, Stainless

"Since this is a thermostatic valve only (no pressure balancing), it responds to temperature changes caused by varying line pressure slower, but it only takes a second or two to compensate. If you have a large reserve of hot water and relatively stable groundwater temperatures, but have other people turning faucets on and off and you don't have a plumbing manifold in your home, you may be better off with a cheaper pressure balance valve. But, if you like the idea of 'set it and forget it', then a thermostatic valve like this is the way to go! Once I initially set my desired shower temperature, I haven't had to change it - I simply turn the 'volume' handle up and enjoy my shower."

Thank you very much.

    Bookmark   November 30, 2012 at 3:42PM
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kmcg

for kirkhall - here's the handle. This is the cheapest one; I like the one mongo posted much more, but this is for a basement bathroom. I plan never to shower there again once our upstairs bath is done!

    Bookmark   November 30, 2012 at 7:21PM
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kmcg

And here's the showerhead. Again, very basic, but everyone likes it so far.

    Bookmark   November 30, 2012 at 7:22PM
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enduring

Thanks Kmcg, for the info and pictures. It looks very nice, and functional. I love functional.

    Bookmark   December 1, 2012 at 10:17AM
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condo_man

Mongoct-

I presently have separate hot & cold shower valves.

I removed the 2.5 gpm restrictor on my shower head, which increases the volume of water for a more enjoyable shower.

Do Symmons-style valves have a restrictor that limits water flow, like my shower head restictor?

Will converting my separate hot & cold shower valves to a Symmons valve have any negative effect on my modified shower head?

Thanks

    Bookmark   January 3, 2015 at 7:31PM
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mongoct

The valve, like all valves, does have an effective GPM pass-through restriction. Half-inch valves are usually around 5-8GPM.

That's not a Symmons restriction. It's sort of like a "water flowing through half-inch pipes" restriction.

Once you replace your current hot and cold valves with the single Symmons valve, there is a set screw that limits the max hot water to cold water ratio that can come out of the valve. That can be adjusted for temperature control.

For volume, no, the Symmons won't negatively restrict your flow. Even with the restrictor removed from the shower head, it's likely that the construction of the unrestricted shower head will still have a lesser volume pass-through than the valve itself.

    Bookmark   January 5, 2015 at 9:39AM
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