Recommendation for a shower control valve

Discussion in 'Shower & Bathtub Forum & Blog' started by jeffrey_m_sutton, Jul 9, 2010.

  1. jeffrey_m_sutton

    jeffrey_m_sutton New Member

    May 10, 2005
    Hi All,

    12 years ago I updated my only full bathroom and bought a Moen (KVK01-01 model number for what that's worth) at Home Depot because I liked the trim and the price was right. Even since I've been plagued with poor water flow in shower and tub despite 65psi of pressure (measured on an outside faucet after the PRV). My measured flow into the tub is about 4.5 gpm - even worse for the shower despite my efforts to 'improve' the shower head. Again for what it's worth I know I have 1/2" supplies into the Moen but I don't recall what's going up to the shower head.

    I am getting ready to convert a half bath into a full bath (well, actually a stand up shower, plus toliet and sink) and I'd like to do better with this new stand up shower. I'm looking for a recommendation for a shower control valve to install because I'm hoping that will make a difference. I've found several sites recommending "It should always be a thermostatic temperature control valve, and preferably a 3/4†thermostat valve."

    It makes sense to me that a 3/4" valve will improve my flow - even with 1/2" supplies. My problem is that I can't seem to find an specs or a way that identifies the size and flow rate of a control valve. Unfortunatley I live in an area without any real plumbing supply companies and my only plumbing source is big box (Depot or Lowe's) and both are very lacking in this type of knowledge.

    Anyways, any and all suggestions are appreciated on what might give me a better shower experience *smile*. Thanks in advance to all who reply !

  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    The capacity of a valve depends on how it is made internally, NOT just the size of the pipes going to it. Most 3/4" valves have internal ports which are SMALLER than a 1/2" pipe. I am not sure what the KVK-01 is, but Moen does NOT make different valves for the various trim parts, so your valve should perform EXACTLY like every other Moen valve, which is NOT a poor flow. You apparently have some other problem, but without being there we cannot tell you what it might be.
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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    All the major manufacturer's websites will provide technical data such as flow rates on their valves. Keep a few things in mind: shower heads are limited to 2.2 gpm, by the shower head itself, and many valves will have a restriction to the shower built into the valve as well. The tub outlet, however, should be full flow and you should be able to achieve 5 to 8 gallons per minute easily

    Avoid the "house brands" and any store. Parts support down the line....unknown.

    Now ,as to type of valve. The valve you have is probably a just turn it and it starts cold and as you continue to turn, the water goes to warm and hot, but there is no change or control of volume. I do prefer a valve which gives you volume control. A thermostatic valve will do that, but they are pricey . A very good option is a valve type which has 2 controls, one for on/off/volume, and another lever for temperature control. The Delta 1700 series is one that I like a lot. You won't find it in the hardware stores, but a plumbing supply will get it. If you have only blue or orange available, they can order it for you.

    For a single shower head, and assuming you have normal household pressure, in the 45 to 65 PSI range, I see no reason to put out $$$ for a 3/4" valve. Piping material does matter. Remember that 1/2" PEX or CPVC are SMALLER ID than copper, so if using those materials, up the pipe to 3/4"
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