Should I have a double check valve and expansion tank with new softener


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Old 01-20-09, 07:42 AM
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Should I have a double check valve and expansion tank with new softener

Hi,
Our plumber has given us a proposal to install a new automatic demand softener with a fleck control valve and sybron high capacity softening resin. Our plumber has recommended that we also install a double check valve and expansion tank to prevent back flow contaminating our softener in the case of a water main break or large use of water supply in the case of a fire. Is this something that would be highly recommended? He proposes charging $200 extra to install this.
 
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Old 01-20-09, 02:29 PM
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The price for that service is not out of the question. The issue would be, is it needed? A check valve will prevent negative pressure causing the softener tank from imploding.

I have only seen this once when a well foot valve failed. I have never seen this on city water nor have I seen an 'expansion' tank on city water for residential use as well.

There may be a reason more than 'watering the stock' in his recommending it. Has this been a problem in the area? is what you want to ask, and get another local opinion.

Andy Christensen, CWS-II
 
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Old 01-20-09, 06:32 PM
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Most softeners these days have upper baskets. This will stop the resin from being sucks out of the tank if the fire department starts pulling water from you home. With a main break, the water simply does not flow in or out. I can see a check valve, maybe. But don't see the need for a double check valve or an expansion tank.
 
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Old 01-20-09, 07:45 PM
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Backflow prevention

Most progressive municipalities require backflow prevention on all new home construction, most notably the RPZ-style of backflow assemblies. The check valve allows unrestricted flow of water INTO the home, so it can't protect you at all from "contamination" at the city level.. These devices are to protect the city from you, not you from your city. Most new water meters have a simple integral check-valve that acts as a rudimentary backflow preventer.

Expansion tanks are usually installed on the inlet to a water heater to protect the softener from hot water expanding to the softener. This device is especially critical if you have backflow prevention, including a check valve at the meter.



Greg Reyneke CWS-VI
 
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Old 01-20-09, 09:14 PM
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Greg, what you are saying sounds like what the plumber was trying to explain to me, and I just couldn't quite get it. Would it protect our softener in the case of a build up of negative pressure in the city water system and to protect the city water system from contamination by the contents of our water softener? Is that why we would want to make this investment?
Bottom line: Would you recommend that we invest in the valve and expansion tank?
If progressive municipalities are requiring this, it sounds like something we should do, right?
 
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Old 01-20-09, 09:38 PM
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Backflow prevention

It is definitely a good idea and is no disadvantages to you at all. $200 for a backflow preventer and a thermal expansion tank is a screamingly good deal. This is definitely not a profit-center for them, but good industry practice.

The backflow preventer really doesn't protect your softener from implosion due to a "negative pressure" event. A vacuum breaker will do that, but since I assume you have a residential system your tank is most likely narrower than 12" where negative presure starts to become an issue, and a vacuum breaker shouldn't be necessary for you at all.

The "concept" of the backflow preventer is to protect the city distribution system from "dirty" water in your home in the event that a "negative pressure" event does occur. For example: in a "worst-case" scenario, you might have a hose full of standing water (or connected to a fertilizer feeder)that could be drawn backwards into the city supply during a negative pressure event. This would obviously be a threat to public health and so the codes now include provisions to protect society at large.

The thermal expansion tank is going to directly protect your softener from heat damage, just make sure that they size it properly for your water heater size and temperature. It is quite common for the hot water in the water heater to "expand" at the end of a heating cycle. The expansion tank will hydro-preumatically buffer this expansion to protect the water heater, your home & your family from potentially catastrophic failure..
 
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Old 01-21-09, 08:58 PM
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Thanks for your advice, Gregg. We will definitely go with the check valve and expansion tank.
This forum is awesome and has helped us tremendously.
Thanks so much!!
 
 

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