Softener Drain Line Question - Size

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Reader90

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Hello All,

Can anyone comment on the impact of having a smaller drain/waste line in my carbon/softener system. I have a two tank, 1.5 cu ft (both 10x54 tanks), one carbon, other resin. The respective drain lines are from each unit are attached to plastic drain tubing, combined after leaving both tanks, then attach to the wall 1/2 inch drain line pipe, but through a 3/8 in. coupler (attached to the 1/2 in pipe)

I ask as the softener loop is plumbed for a drain line at 1/2 inch at the wall/softener loop area. The installer (assuming lazy) downsized the 1/2 inch drain line at wall to 3/8 -- I assume because he did not have any 1/2 inch drain line tubing. I will be correcting this.

Asking to know if the smaller size of the drain line, does this impact the effectiveness of the backwash process at all?

Thanks in advance!!
 

ditttohead

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Too complex to answer in a forum, it comes down to a lot of boring math but in general, do not downsize the drain pipe. A 10" carbon backwashing system should flow about 5 GPM to the drain. The velocity of 5 GPM through a 3/8" tube would be very high and likely very noisy. My charts say it is possible to flow that amount of water but is certainly not advisable.
 

Reach4

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Too complex to answer in a forum, it comes down to a lot of boring math but in general, do not downsize the drain pipe.
I originally had suspected the post to mean there was a nominal 1/2 inch tee fitting combining 1/2 inch drain lines. This tee had an estimated 3/8 inch ID.

Now I see that I interpreted incorrectly. Reading again, it is made clear by the second paragraph that actual 3/8 ID tubing is going through the wall. I expect the softener, with its 2.4 gpm of flow does not have a problem, but that cannot be said for the carbon tank.
 

Reader90

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The drain line plumbed into the house at the wall is 1/2 inch. Last installer reduced it to 3/8 inch. Current drain lines from both softener/carbon tank is also at 3/8 inch currently. I am going to remove the 3/8 inch copper fitting on the home drain line pipe and rework all drain line tubes to 1/2 inch this weekend.
 
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