Introduction: Fitting a T33 Rainwater Diverter and Filter for Water Butts

There is a fine product out there called a Raintec T33 Rainwater Filter, made by It  filters the water coming out of your downpipe so that only clean rainwater enters your water butt; leaves and other debris continue down the pipe as normal.

Trouble is the English instructions included are the direst I have ever seen. Sample:

“3. Instll Filter choose reduction according to downpipe diameter not required
reductions should be cut out with a sharp knife top  fixpart of filter in the downpipe see Fig 3. 3.”

So here's my alternative guide.

You'll also find this product variously called Regenwasser-Fallrohrfilter T 33 , Regenfilter,RF-T33, Regenwachter, and so on. As of April 2010, it's listed on

Step 1: Caveats

These instructions were written by a user as a substitute for the ones included in the pack. Much of the technical information is culled from various supplier websites, so the writer cannot vouch for its accuracy. The installation instructions are the writer’s best attempt: again, he cannot be liable for any errors or omissions. Your problems are your own. Good luck.

Step 2: Blurb

The T33 Downpipe Rain Filter Unit is suitable for water butts or tanks up to 1000 litres, and a roof area of 80 m² (there is another version, the T50, for roof areas of 100 m²). It  filters the water through a 0.1mm gauge stainless steel screen, so that only clean rainwater enters the butt, while leaves and other debris continue down the pipe as normal.

The T33 is available in brown or silver, and is suitable for round downpipes measuring 63mm, 68mm, 80mm or 100mm, and for square downpipes measuring 61mm or 65mm. A long hose is included so you can site your waterbutt further from the downpipe if you want to.

The filter unit allows 90% of the water to pass to the butt, ensuring quick filling even with only light rainfall.

If the filter unit is correctly installed at the right height, the butt will only fill to the top, avoiding overflows. The bottom of the filter unit should be approx 5cm below the top edge of the water butt: the butt will only be filled to this level, and thereafter water will be directed straight down the downpipe.

Step 3: Bits and Pieces

Here's what should be in the box

Step 4: Siting Your Water Butt

Before you start to install the rainwater filter, you need to have your water butt in place in its final position. Remember that the hose (either long or short) will need to stretch from the downpipe to the butt.

If you don’t have a stand for your water butt, jack it up on some concrete blocks or something, so you will be able to get your watering can under the tap. Remember when full it will be HEAVY: a litre of water weighs a kilo, so a 250-litre butt will weigh at least 250kg.

You can of course link up more than one water butt. Connect additional butts at the high water marks of each one; if you connect the water butts at the bottom, debris may accumulate over time - even with the filter in place - and block the connecting tube.

When the first water butt in the chain is full, water will start to flow into the second water butt. More butts can be added to the chain in exactly the same way. You’ll need a tap for each water butt in the chain.

You can find more instructions on linking water butts online.

Step 5: Installing the T33 - Tools

 You will need:

  - a spirit level
  - a drill with a 32mm bit
 - a saw and /or craft knife
  - sandpaper or a sander 
  - determination

Step 6: 1. Preparing the Downpipe

Take off the lid of the water butt if it has one. Mark the height of the top of the water butt on the downpipe using a spirit level; from this point measure 15cm upwards, and make a mark. Now measure 5cm downwards, and make a mark. The butt will only be filled to this level.

Cut the downpipe at the top and bottom marks and remove the 20cm section.

Step 7: 2. Preparing the Bottom Section of the Filter Unit

Marry up the bottom half of the filter unit with the pipe (use the 20cm section you have cut out as a template).

Cut away as many of the plastic flanges and lugs as needed to allow the base of the bottom section to fit snugly into the pipe. Don’t cut away too much, or, once fitted, the filter unit will wobble about in the downpipe.

I cut the corners off mine, but I could probably have managed just sanding the corners down till they fitted. That way, it might have fitted more securely in the downpipe. Try it.

Step 8: 3. Fit the Hose to the Filter Unit Outlet

It is easier to fit the hose onto the outlet at this stage than once the filter unit is installed in the downpipe. Choose either the short or long hose, depending on the distance from downpipe to water butt.

Check that the hose will fit onto the outlet from the bottom section. Mine didn’t. Boo-hoo. Sand the edge of the outlet until it does, and push it firmly on.

Step 9: 4. Fit the Filter Screen

Push the filter screen down into the bottom section of the filter unit and check it is secure - it should clip in firmly.

Step 10: 5. Preparing the Top Section of the Filter Unit


Now repeat the bodging process for the lid of the top half of the filter unit.

Step 11: 6. Fit the Filter Unit Into the Downpipe

Push the lid onto the hanging down bit of the downpipe.

Push the bottom part of the filter unit as far as it will go into the sticking up bit of the downpipe.
Push the top part of the filter unit upwards onto the hanging down bit of downpipe.

Press the top part of the filter unit down onto the bottom part; slide the lid down on top of the top part.

If it wobbles about, you may need to fix the downpipe to the wall with another downpipe clip. Make sure the clip is at least 12cm above the top of the filter unit so that you can get inside it if needed.

(Apparently the rubber seal part can be fitted to the bottom edge of the downpipe. Why you would want to do that I’m not sure - and the makers aren’t saying.)

Step 12: 7. Preparing the Water Butt

 Cut a hole in the water butt with a 32mm drill. The hole needs to be below the bottom of the filter unit - check with a spirit level if necessary.

Push the threaded part of the connector through from the outside. Secure it with the rubber washer and the fixing ring from the inside. Tighten.

Step 13: 8. Connect the Hose to the Butt

Now connect the hose from the bottom of the filter unit to the butt.

Step 14: Odds and Sods 1

There’s still some bits left over including a wire clippy thing. I’m not sure what it’s for, but here’s a picture from the manufacturers’ website, It might give you a clue (it doesn’t me).

Step 15: Odds and Sods 2

The other bits left over are some hose clips. You will only need to use these if you are connecting the hose to butt connectors smaller than 32mm - eg maybe you already have a 28mm one installed in the butt and don’t want to remove it.

Step 16: Maintenance

The filter screen is designed to clean itself, but if it gets blocked up, simply detach the two parts of the filter unit, slide the upper part upwards, take out the filter screen and run it under a tap, or brush it clean with a soft brush, then pop it back in.

If you prefer to keep your butt empty in winter, (maybe you don’t want the water to freeze and possibly damage the butt), open up the filter unit (detach the two parts of the filter unit, slide the upper part upwards) and push the winter plug into the top of the outlet pipe that goes to the butt.

 After each frost period, check that the filter unit is still correctly fitted in the downpipe.

Step 17: Oh Come On! It Can't Be That Bad!

The original instructions?

OK, Smartypants. If you can make sense of this:

“3. Instll Filter choose reduction according to downpipe diameter not required

reductions should be cut out with a sharp knife top  fixpart of filter in the downpipe see Fig 3. 3.”


- then by all means use the original instructions pictured. They're on a pdf here too.

Or you could translate the German instructions (another pdf). I only did a year of German at school, but that was enough to tell me that these instructions are almost as little use as the 'English' ones.

Step 18: And Finally...

If the instructions are so dire, why not contact the people who sold you the filter and get them to supply proper ones?

Great idea. Or so I thought.

If it amuses you, you can read the text of my email correspondence.   Here's a little scorecard:

My emails to them: 6
Theirs to me: 2

My phone calls to them: 1
Theirs to me: 0

My attempts to translate it: 2
Theirs: 0

My complaint about lack of service: 1
Their sarcastic reply telling me to bog off: 1

I hope this instructable will be of some use to somebody. Toodle-pip.