Underground 110/160mm Non-Return Valve Installation Guide

A step-by-step guide to installing your underground Non Return Valve - the only adaptable NRV with options for 160mm & 110mm pipes, plus an inspection chamber.

The underground 110/160mm NRV can require a more advanced installation. Therefore the user must be a very competent DIY'er, or at least have some experience in ground & pipe works. The below is advice only.

A good first step is to first assess the depth of the pipe underground. You can do this by lifting the nearest manhole chamber lid. The inlet feeds will indicate the depth below ground level. 

If you have a relatively shallow pipe, this will aide installation & reduce risk. However, if you're pipe is deeper than expected, contact a professional - or consider a 110 Pushfit or Toilet Bung.

Step 1: Locate the position for where you will house your NRV. This will be somewhere between your property exterior wall (usually close to the downstairs toilet), & your exterior manhole chamber. Mostly, this is a straight line.

If there is not enough space available, you can consider the 110 Pushfit NRV or a Toiler Bung.

We strongly advise using the necessary equipment to locate any pipes, mains or feeds beneath the area you intent to dig before beginning.

Step 2: Once you have taken the necessary steps to allow safe excavation, mark the area to be dug. This will be larger than your NRV, as well as allowing for space to cut & connect to the underground pipe.

Assess the type of ground you will be removing, & consider the future reinstatement (such as gravel, slabs or paving).

Step 3: Neatly excavate your top layer, taking care to cut along joints if removing patio or similar.

Then continue to carefully remove earth & sub-base debris, taking care to note any pipes or obstructions along the way. Continue until you expose the pipe.

Place debris to the side as some of this can be refilled.

Step 4: At this stage, ensure no-one uses the toilet as you will be cutting the pipe.

You may need to dig around the pipe some more so you can safely get your cutting tool of choice around the pipe.

Mark the area to be cut, taking into account any reducers or joints required. Then cut your pipe in a straight line, taking extra care with clay pipes as these can chip easily.

Step 5: Fit your NRV, including any reducers and joints, utilising & tightening any jubilee clips required. Be sure to place facing the correct way, else you will cause an ugly blockage.

You can then test the flow and seal by flushing the toilet a couple of times, & even pouring extra water down the toilet to increase flow.

Address any seepage.

Step 6: Back fill the bottom of the pipe with pea gravel until the pipe only is covered, leaving the top of the inspection chamber clear.

Step 7: Install your risers onto your NRV all the way to the top of to-be-finished ground level.

Then, using your manhole chamber of choice, trim the top riser down to the required height so you manhole chamber will sit flush with the ground level.

Step 8: Using your previously excavated earth, back-fill around the risers, compacting as your go to avoid future settlement.

Fill right up to the level needed before you complete any required sub-base for your ground level finish.

Step 9: Complete the required sub-based, fit and place your manhole chamber in position, & reinstate your ground, providing a neat finish around your new manhole chamber.

Once set, you can test removing the lid, and accessing the inspection chamber to practise maintenance of your underground NRV.