Drain size for kdf and carbon back washing filters

[EIR]

Planning on a back washing carbon filter and possibly a kdf unit before the carbon. On municple water.

My initial plan was to utilize an existing washer standpipe for backwash disposal of both. Realizing a 7" kdf tank could see 10gpm backwash had me wondering if a 2" drain could handle the flow (still trying to determine if my supply can handle that).

I would probably like to add a new utility sink for these. Does anyone make a plastic wash sink that will accept a 3" drain? Or could I just plumb a 3" p trap in and use a 4" to 3" reducing fitting as a funnel/ air gap?

Secondly, my municple water is currently has a 3/4" copper main coming into the home at 65psi.

a rough distance to the water shut-off at the street is roughly 60ft from my main shutoff valve inside.

What max GPM could I expect or would it be best to do a bucket fill test?

 

[Bannerman]

had me wondering if a 2" drain could handle the flow

Many homes are equipped with 1.5 drains from sinks and washer standpipes. If you have 2", that is a bonus and I doubt an unrestricted 2" drain would present a problem. Each back washing filter needs to be programmed so they don't backwash at the same time regardless.

Does anyone make a plastic wash sink that will accept a 3" drain? - Or could I just plumb a 3" p trap in and use a 4" to 3" reducing fitting as a funnel/ air gap?

If you're planning on draining into a sink, keeping each drain pipe discharge above the rim of the sink will act as an air gap. Nothing else would be required.

Bucket test required as each elbow, tee and valve will vary the rate.

 

[Sponsor]

 

[ditttohead]

Your 3/4" main will easily accommodate the system. The flow rate of 3/4" pipe is actually a velocity issue. Velocities should be kept less than 8 feet per second. I don't have my chart in front of me but I am guessing 10 GPM would be fine. Flow rates in excess of that over a long time can cause pipe damage but this may not manifest itself for many years. Intermittent and infrequent flow rates exceeding 8 FPS would likely not do any damage.

 

[EIR]

I planned on either adding a utility sink or some kind of air gap drain arrangement to accomdate these units.

My washer standpipe is new and up to code @ 2" PVC meeting all the other UPC code requirements as well.

I would sleep easier knowing these high flow backwashes were going into either

1)way oversized drain with no way of backing up under normal conditions or
2)a utility sink with a 2" to 3" drain which would give it some wiggle room if for some reason the drain couldn't keep up.

When plumbing this units in my plan was mainshutoff--->meter--->manifold for hose bibs--->water treatment---->manifold for cold water supplies--->water heater feed.

Should I swap the water heater and cold water tap supplies' positions?

 

[polychromeuganda]

You should have no difficulty creating an air gap just terminating the backwash line into 2" with some vertical above a trap. I would think 1.5" would also be fine. Any problems with the line capacity between there and the street will be the only thing to watch for a gotcha. If it solves a problem, you may not be required to send clean water to waste treatment or a septic system, check your local rules.
I send well over 60 gpm down a 2" line to a surface drain with an air gap when I backwash a pool filter a few times a year. The air gap is not normal or required for such a line it's a workaround for a failed dedicated line. That matches flow capacities I see online like this one: https://flexpvc.com/Reference/WaterFlowBasedOnPipeSize.shtml
... and I think you were referring to pipe layout, but in case it was a more general thought, if you put in a utility sink, don't swap the hot and cold. The sink is something we all do on autopilot. you'll be forever scalding yourself.

 

[EIR]

Thanks for the response. I see that I wasn't understanding the true capacity of gravity drains (green column).

I also discovered various air gap fittings to facilitate a clean install.

 

[ditttohead]

 

[ditttohead]

 

[EIR]

I haven't been contacted yet by your guy.

What's your view on this. Looking for 4-5gpm service flow.

8x35 kdf tank
Two 10x35 or 10x40 gac in parallel

I am considering an anti scaling media before the hot water heater.
Do any of them work?
I wouldn't mind trying the polyphosphate filters but I don't want baby cartridges, i d want a small media tank and bulk media but have been difficulty finding that online. Am considering Watts scalenet but that seems so hyped and not sure any of them actually work.

 

[ditttohead]

The 12x35 single GAC will give you very acceptable performance in a single tank configuration at 4-5 GPM. It gets difficult to gauge performance but in general you will get acceptable performance in the 3-4 GPM range per cf, the 12x35 can be filled with 1.5 cf with a heavy top screen and proper design. Adding a second tank is unlikely to add any performance gain. It might make more sense to use a larger diameter short tank rather than two wide tanks. Enpress makes a great 16x33 tank.

As to the Scalenet... we sell nearly identical systems... I have done extensive testing of all of these medias including many other salt free technologies. In a wetted environment the polyphosphate systems seem to work best for tankless and tank heaters if soft water is not possible or desired. The anti-scale medias would come next but their performance is very hit and miss. We just had a large customer pull out a dozen of the system mentioned above after a 1 month test in one of the biggest animation companies facility. All failed, all were removed, and salt softeners were reinstalled in all locations. We have had other places where they were successful.
The problem is the literature nearly guarantees that these will work as well as a softener, this is simply not the case. Real world experience and extensive testing has shown us that they do work sometimes reasonably well. They never work as well as a real softener.

Hope this helps.