Sharing vs Non sharing and why can't CA have it?

March 5, 2020
...how much do you really know about the valves behind the wall that power your shower system?

Most of us don't really think that much about what goes behind our plumbing fixtures until we having to purchase a new one.  With showers we are very familiar with the handles and the shower head and the tub spout for example, but how much do you know about the valve behind the wall that powers the whole system?  If your answer is nothing at all, you are not alone!  

There is a lot to learn and understand to make the most informed decision when choosing a new shower system and this article focuses on the question of sharing and non-sharing valves.  What are they, why should you choose one over the other and why are they restricted in some states?

First, let's discuss what they are.  Think about a shower system.  Older, traditional tub/shower systems typically had a shower head and a tub spout.  Usually when you turn the handle, the water comes out of the tub spout and to move or divert the water up to the shower head you pull a lever on the tub spout.  This diverts the water upwards until the water is turned off.  This is a very economical and practical system, but it doesn't provide many options and many diverter tub spouts are less attractive than non-diverting ones.  

Newer systems may have not only the shower head and tub spout, but also wisely feature a hand held shower wand, which we regularly tell anyone who will listen, should be standard with all shower systems installed.  (Click here for more on that topic).  If you have a non-sharing valve, you will be able to use either the shower head OR the hand shower at one time. 

If you have a sharing valve, there is a position on the valve allowing you to have water going to both the shower head and the hand shower at the same time. 

This works with any of your shower elements, so it could mean two shower heads working at once, a shower head and body sprays etc.  It just means that more than one shower element (or component) can essentially share the water at one time.  

OK, that's the what, now for the deeper dive.  If sharing valves exist, why would you not want one?  Well, there are a few reasons:

  • Water saving:  As we know, we have a limited supply of fresh water on this planet, and as the population grows it becomes more and more important to save and protect it.  North America certainly seems ahead of the curve on this one, (evidenced by the enormous water wasting shower heads shown at the biggest plumbing shows in Europe last year). The state of California actually outlaws the use of sharing valves for just this reason; water is precious and we need to safeguard it. 
  • Limited hot water:  Just how big IS your hot water tank?  With limitations on the flow rate of each element in your shower, you could use multiple elements longer than you used to be able to, but it will still significantly lessen the length of your time with a hot shower!
  • Personal preferences: While it seems like a great idea, do you really want want spraying at your from all different directions?  If you take the time to direct them properly, maybe.  But it tends to be one of those things that sounds better in theory than in practice.

The Pro's:

Why would you want a sharing valve?

  • Maybe two of you like to shower at the same time.  In that case, two functioning shower heads could be great.  (Make sure you have adequate available hot water!)
  • You might really like/want to have multiple sprays of water working at once.  For example, if you have an elderly person in a shower seat, and the hand shower is being used to wash hair, maybe having the overhead shower at the same time helps to keep the person warmer.  

There may be other perfectly good reasons, but before deciding which is right for you, make sure to check out the code restrictions in your area!  If you are in an area that does not allow for sharing valves, you could be asked to change them out before receiving final plumbing approval.  If codes allow you to have sharing, ask yourself, is this the kind of shower system that I really want; do I have enough hot water to make it useful and lastly, does it make sense from an environmental standpoint.  

Once you understand the differences, the choice is up to you. 

What are the pro's and cons of sharing vs. non-sharing shower valves?