Mash Tun Fly Sparge Float Switch

On our last brew day, our Mash Tun over-filled with water during the Fly Sparge.  I knew there was a way to rectify this, so I set out to do just that.  And then some.  Our 70 quart Coleman Xtreme Mash Tun Cooler didn’t have a sparge assembly, and I decided to fix that at the same time.  This is a very popular cooler to use as a Mash Tun, so I will provide the measurements for the sparge assembly.

Parts list:

Float switch assembly:

uxcell Aquarium Wired Liquid Water Level Sensor Float Switch – $4.95
Spears 439 Series PVC Pipe Fitting, Bushing, Schedule 40, 1/2″ NPT Male x 1/8″ NPT Female – $3.93

Home Depot:
1/2 in. CPVC CTS Slip x FPT Female Adapter – $1.19

This is all I purchased for this assembly.  The elbow, CPVC and DC connectors were all leftover from other projects. (All CPVC was left over from the sparge assembly).

Total Float Switch Cost:  $10.07

Sparge Assembly:

Home Depot:
1/2 in. x 10 ft. CPVC SDR11 Flowguard Gold Pipe – $3.65
1/2 in. CPVC CTS 90-Degree Slip x Slip Elbow (10-Pack) – $1.97
1/2 in. CPVC CTS Slip x Slip x Slip Tee (10-Pack) – $1.79
1/2 in. CPVC CTS Slip Cap – $0.21
1/2 in. CPVC CTS Slip x MPT Male Adapter – $0.25

Bargain Fittings:
1/2″ STAINLESS Quick Disconnect – Male x 1/2″ NPT FEMALE – $8.99

I bought this a while ago, so I didn’t have shipping on this one. has a flat rate $5.00 shipping charge.

Total Sparge Assembly Cost:  $16.86 – As you can see the bulk of the cost is the Quick Disconnect

Total project cost:  $26.93

This is the Float switch picture next to the 1/2″ x 1/8″ bushing.  The O-ring and washer were taken off the wired end of the switch.

Added about 6 wraps of plumber’s tape to the switch

Tightened the bushing on the switch.  Two adjustable wrenches help out with this.

Top view of the switch.  You can see that the switch itself is sealed, not allowing water in.

The 1/2″ slip to female NPT adapter come packaged in a bag with a gasket.  Be sure to put the gasket into the threaded end of the adapter.

Voila.  The assembled switch assembly (Pre-Installation assembly).

The host:  A 70 quart Coleman Xtreme Cooler Mash Tun.  You can see the Mash Tun Conversion HERE

You can see where I drilled out the holes for the sparge assembly and the float switch.  I determined the hole placement once I had the rough sparge assembly put together.  The float switch was placed in an existing dimple that did not interfere with the sparge assembly.

Top view.  NOTE that when drilling through the lid of this cooler, it is not like to round coolers.  The lid is not hollow.  It is insulated with styrofoam and can make quite the mess if drilled indoors as I did.

Sparge Assembly rough fit on top of the cooler.  You can see that the assembly itself uses only three different lengths of CPVC:

12 15/16″ for the three long spans
4 3/8″ for the eight ‘side’ spans
3 5/16″ for the four short connecting lengths

The vertical arms can vary depending on the height you want the assembly installed.  Mine are 3.75″ tall.

Test fit:

Test fit with Float Switch:

Showing where Float Switch sits:

Full underside of lid:

Drilled a random pattern of 3/8″ holes on the TOP side of the assembly.  I did not drill the vertical arms that will install into the lid.
 Here’s how the switch is installed:

I placed the switch at the height I wanted and marked the CPVC that is pushed through the lid.  I then cut the CPVC to allow for the elbow to sit at that line.

Soaking all  the parts in a Bar Keeper’s Friend bath.

These are the pigtails that I had.  I got 10 sets from Amazon for less than $9.00 for another project on which I only needed a few.

Soldered a length of wire and the male pigtail to the switch long enough to connect to the pump wiring

Snipped the + (red) power wire to the pump and soldered the female pigtail in place.

Heatshrink: it matters

Connected the male and female pigtails together.

Next, I am going to make a terminator.  This is so I can run the pump when NOT using the float switch.  I have some male DC Connectors left over from the 12v Pumps.  Funny how it’s less expensive to buy a 10-pack instead if individually.

I unscrewed the sleeve and attached a wire through both posts.

Soldered the wire onto both posts

I put a length of speaker wire through the strain relief on the sleeve and screwed the sleeve back on to the connector.

I then melted a length of heatshrink to the sleeve.  Now I know for certain that this is my terminator.

I have tested the switch and the terminator.  The pump DOES turn off when the float reaches the apex of the switch.  Placing the terminator in-line allows the pump to run, thereby bypassing the switch.

I then sealed the holes using food grade silicone caulk that I had left over from installing a sink.

This was the hardest to get to and clean up.  It’s the left connection for the sparge assembly.

This was by far the easiest to seal and clean up.  This is the connection for the Float Switch.

And there you have it.  A sparge assembly and float switch for less than $30.

Leave a Reply