Liberty pump question about drainwater temps

16 years ago

Hi, I am installing a utility sink in my basement and my washing machine will drain into it. I will be using a Liberty pump to pump the water out. I have a Maytag washer model MFW9700SQ1 that has a "sanitary cycle" which heats the water to around 150 degrees. The Liberty pump model 404 is good to 140 degrees drain water temp and the Liberty model 405 is good to 180 degrees.

Do you think I would be able to use the 404 without failure? The 404 uses 1 1/2" fittings vs. the 405's 2" fittings. I would like to stay with the 1 1/2" fittings if possible. Thanks for any advice.

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Comments (3)

zl700
15 years ago
The waste water heated to 150 degrees will not be at that temp once drained into the laundry tub. Due to the heat sink of the washer, the clothes, tub, pipes, etc. The temp will have been lowered by then.

Make sure you size the pump based on pipe distance, head (pipe length, height, fittings) to select one that will not short cycle but keep up with discharge of washer and capacity of the tub combined.

Go with the smaller one if the specs on performance match your needs, dont worry about temps.
lazypup
15 years ago
In regards to the temperature I would agree wholeheartedly with what zl700 has previously posted, although after checking out the performance curve on both the Liberty Pump model 404 & 405 I am not convinced that either of those pumps would be a good choice for your application.

As zl700 already pointed out, the pump must be sized to keep pace with the rate of discharge but not be over sized. Over sizing a pump will result in the pump repeatedly starting and stopping in a condition we call "short cycling".

On initial startup an electric motor momentarily draws what is technically referred to as LRA (locked rotor amperage) which is typically 3 times the FLA (full load amperage) of the motor. If the motor is repeatedly started and stopped it results in excessive heat buildup in the motor winding and premature motor failure.

In general submersible pumps are intended to be cooled by the liquid surrounding the motor casing. In this situation the buildup of heat would be further exacerbated by the temperature of the water being pumped.

Rather than the Liberty pump I would much prefer to recommend a Saniflow "Sanivite" pump, which is designed specifically to receive the discharge from dishwashers or laundry equipment where the water temperatures are in a higher range.

Sanivite.by Saniflo

$259.00
http://www.sanifloproducts.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=SP&Product_Code=SANIVITE&Category_Code=SP2

However, before you select any pump for this application you must do your homework very carefully.

Even though the pumps may have an 1-1/2" or 2" discharge line, that does not mean that it may be discharged into a 2" ro even a 3" gravity flow line in your house DWV system.

Under the IRC (International Residential Code) the gravity flow line receiving the discharge must be able to assume an additional load equal to 1.5DFU's (drainage fixture units) for each gallon per minute of the pump discharge or 14.2gpm, whichever is greater. Under the UPC (Uniform Plumbing Code) we must compute at 2DFU's per GPM or 20gpm, whichever is greater.

Once we have the DFU rating for the pump we must also compute the existing DFU load on the receiving line and add to two values together to determine the combined DFU load.

IN both instances the DFU load of the pump itself will generally exceed the maximum permissible DFU load on a 3" horizontal branch line under gravity flow, not to mention what the existing load on that line may be.

IN nearly all instances, unless your house has a 4" main drain you will not be able to install a pumped discharge.

The next point that you must consider is that the code requires the pump to be fully enclosed in a water tight vessel, and the vessel MUST BE vented vented through the roof with a dedicated vent. (The vent may not be attached to any other vent in the structure)
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kardev1_gmail_com
14 years ago
If it's of any help, when I recently replaced an old Maytag front-load washer with a Samsung WF448AAW that has a 150 degree sanitize wash cycle, my two year old sump pump shut down the first time I used the cycle. Bypassing the float switch wouldn't start the pump. Only after the water cooled down did the pump restart.

My pump is a Little Giant 8E-CIM in a Little Giant Drainosaur WRS-8E (model #509150)wastewater pump system. The pump is rated at 140 degrees. The vertical float is rated at 125. Tech Support at Little Giant told me that yes, the water temp could definitely have overheated the pump. They also told me that the Drainosaur tank itself is only rated at 125 degrees, though quite frankly, I doubt that would ever be a problem.

The pump was problem-free before using that sanitize cycle (I do regular cleaning maintenance on it) and it's been problem-free for a week now since the incident.

Although there's things I don't care for on the Liberty Pumps 405 unit, it's currently the only complete packaged unit out there rated for anything over 140 degrees. You can easily find individual pumps for high temps, but not a complete pump system unit (tank, pump and float). The Grainger catalog lists a couple dozen wastewater pump systems,but only the 405 has a rating higher than 140 degrees.

Liberty pump question about drainwater temps

Comments (3)

zl700

lazypup

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