# Plumbing question: replacement for mixing valve? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [September 27, 2014, 7:28pm UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732 "2014-09-27T19:28:04Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [September 27, 2014, 7:28pm UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/1 "2014-09-27T19:28:04Z")
(Hey, what happened to the Barn House subforum?) Anyway - my house has a combined boiler/water heater, oil fueled, for hydronic heating and household hot water. Like most such “tankless” systems, it has a thermostatic mixing valve to deliver a more pre-regulated hot water supply from the 170-180 degree heating tank level. It’s FUBAR. It slowly failed over last winter, leaving us with colder and colder hot water, until I figured out the system and adjusted it, in which course the knob broke off the stem and the adjustment was ratchety at best. I found a comfortable setting that worked until now… and now it’s mixing about 10% hot, just enough to keep the water from being groundwater-icy. It is NOT warm enough for showers. Brrrr. Since it involves about ten soldered copper joints, is closely coupled to the boiler/heater and is the lowest point in three stories of plumbing, I am calling in a pro on Monday rather than fix it myself. Here’s the actual question: Are there better and worse brands and makes? Is there an industrial-grade maker and model I should ask for? And is there any better, more reliable, more modern tech this bronze-age bit can be replaced with? ---
**Author:** ![MikeG](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikeg/32/4329_2.png) [@MikeG](https://boards.straightdope.com/u/MikeG)\ **Post date:** [September 27, 2014, 10:07pm UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/2 "2014-09-27T22:07:30Z")
Stick with Watts. Excellent quality and a wide network of dealers. ---
**Author:** ![MikeG](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikeg/32/4329_2.png) [@MikeG](https://boards.straightdope.com/u/MikeG)\ **Post date:** [September 27, 2014, 10:08pm UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/3 "2014-09-27T22:08:36Z")
If you are in Chicago PM me for a plumber referral. ---
**Author:** ![DingoelGringo](https://avatars.discourse-cdn.com/v4/letter/d/9d8465/32.png) [@DingoelGringo](https://boards.straightdope.com/u/DingoelGringo)\ **Post date:** [September 27, 2014, 10:10pm UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/4 "2014-09-27T22:10:53Z")
I’d suggest you call a real plumber instead of trying it yourself. Retired Plumber ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [September 27, 2014, 10:47pm UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/5 "2014-09-27T22:47:59Z")
> [@MikeG](#): > > Stick with Watts. Excellent quality and a wide network of dealers. That’s what I guessed from poking around. There are a couple of good industrial brands but for light use and residential, it’s Watts. > [@DingoelGringo](#): > > I’d suggest you call a real plumber instead of trying it yourself. I already noted that I was, thanks. I am a very experienced remodeler and general handyman, but the combination of issues makes me leery of tackling it. For one (more) thing, the incoming cold water and outgoing hot water lines are 3/4 inch, and it looks like someone went to extraordinary trouble to fit a 1/2 inch valve. From a reducer on the cold line to a reducer on the hot line, there must be 20 pieces of soldered copper to connect the smaller valve. AFAICT the heater loop connectors are half inch, but under normal circumstances that loop would only provide about 2/3 of the total flow anyway, probably less. I am going to ask the plumber to replace the whole thing with a 3/4 inch valve and matching plumbing. This house is still pretty much as-built 10 years ago, and while it’s generally quality work there’s still a lot of “builder’s shit” to be replaced. Can anyone think of a reason they would have gone to such lengths to put in a smaller valve - other than that it was a little cheaper and they had it and the fittings on the installation day? ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [September 27, 2014, 10:54pm UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/6 "2014-09-27T22:54:26Z")
And while we’re at it… I guess technically this is a tempering valve rather than a thermostatic mixing valve. Can anyone explain the difference? It is at the head of the hot water supply system, not at a point of use location; that’s the only difference I can seem to find. What’s the diff? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [September 28, 2014, 12:25am UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/7 "2014-09-28T00:25:34Z")
by having one valve at the start of the domestic hot water system then all the pipes and the water in them are at a safe temperature. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [September 28, 2014, 12:32am UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/8 "2014-09-28T00:32:55Z")
> [@johnpost](#): > > by having one valve at the start of the domestic hot water system then all the pipes and the water in them are at a safe temperature. I understand the purpose of thermostatic valves - I’ve had or put them in showers for more than a decade. The question is: what’s the difference between a “tempering valve,” which seems to be what I have and goes at the head of the hot water delivery system, and a “thermostatic balancing valve,” which is different in some way but appears to be the same machine for the same purpose. ---
**Author:** ![Count\_Blucher](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@Count\_Blucher](https://boards.straightdope.com/u/Count_Blucher)\ **Post date:** [September 28, 2014, 12:36am UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/9 "2014-09-28T00:36:24Z")
Many utilities sell these now (your state may vary). My understanding is that the utility doesn’t make money on the install, but on the service calls and the monthly service contract incorporated into the bill. Only the OP can say whether its worth a monthly fee to make sure this thing works, but repairs will certainly be a service call now. So, cash to the plumber or put it on your utility bill…? ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [September 28, 2014, 1:02am UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/10 "2014-09-28T01:02:05Z")
> [@Count\_Blucher](#): > > Many utilities sell these now (your state may vary). My understanding is that the utility doesn’t make money on the install, but on the service calls and the monthly service contract incorporated into the bill. > Only the OP can say whether its worth a monthly fee to make sure this thing works, but repairs will certainly be a service call now. > > So, cash to the plumber or put it on your utility bill…? We don’t have utility bills. 🙂 ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [September 28, 2014, 1:25am UTC](https://boards.straightdope.com/t/plumbing-question-replacement-for-mixing-valve/699732/11 "2014-09-28T01:25:44Z")
> [@Amateur\_Barbarian](#): > > I understand the purpose of thermostatic valves - I’ve had or put them in showers for more than a decade. > > The question is: what’s the difference between a “tempering valve,” which seems to be what I have and goes at the head of the hot water delivery system, and a “thermostatic balancing valve,” which is different in some way but appears to be the same machine for the same purpose. your sinks throughout the house even with separate faucets won’t put out scalding water.