I want to add a new en suite but do I need a new sewer connection?

Property Clinic: Significant expenses associated with a second waste connection

The cost of installing an additional waste connection for an en suite could prove to be prohibitive. Photograph: iStock

The cost of installing an additional waste connection for an en suite could prove to be prohibitive. Photograph: iStock


I would like to build an en suite in the first-floor front room of my property.

The sewer connection is in the back garden. I would like to add another sewer connection in the front of the property. How can I find where the connection is? Who is responsible for creating the connection? How long can it take? How much should I budget for this work?

The alternative would be an up-flush toilet, but it’s not an option I would like to take.

Routing a new waste pipe in an existing building to get to the main sewer line can be disruptive and costly and can mean carrying out repairs and decoration to numerous rooms in order to facilitate the pipe run. Finding the least disruptive and most cost-effective way in existing properties is one of those conundrums which is likely to leave you scratching your head.

I note that your proposal is to put an en suite in the first-floor front room of your property. As a waste pipe would have to run across much of the property to make a connection in the back garden, you are proposing to add a new connection within the front garden. However, your suggestion is not a proposal without its own complications.

In my experience, in most developments and urban centres there is generally only one sewer line serving a property and these are normally along the front access road or along the rear of the property – and the position/arrangements generally depend on the age of the house/network and the nature of the developer at the time.

It would be rare to have a sewer pipe to both the front and the rear of a property for a mains connection unless you have a public road bounding more than one part of your site.

To find out whether a second connection is possible in the first instance, you will have to make contact with the drainage division in your local authority to find out where the sewer lines are in and around your property.

They should be able to provide you with a map/information on the location of such drainage networks also. Assuming there is an alternative drainage line to the front of your house, you will need to make an application for a connection to the managing authority. They in turn will advise on the procedure for making the connection – whether your own builder can make a connection or if the managing authority’s own nominated contractor must carry out this work.

In either scenario, I anticipate that there would be significant costs associated with a second connection of this nature – likely to be thousands of euro alone – and would seem to me that the cost for this would outweigh the potential benefit of adding the en suite.

Before you seek a second connection, you should do some further investigation. Firstly, you should check whether there is a suspended timber floor at the ground-floor level within your house. If there is a suspended timber ground floor, it would be quite easy to take an acoustic waste pipe down through the house and under the suspended timber floor and connect at the rear garden.

Alternatively, you should have a look at which way the joists are spanning at first-floor level.

If the joists are spanning the house from front to rear, you may be able to provide a waste pipe within the first-floor structure which could be directed to the rear of the house and, again, this would eradicate the need for a separate connection to the front of the house.

Alternatively, you could also consider taking a waste pipe down through the first floor and mounting it at a ceiling /wall junction at the underside of the ceiling at the ground floor. This could be encased with acoustic sundry boxing and could be part concealed using a decorative cornice.

Depending on how favourable the above investigations are, as a last option you could consider having a CCTV survey carried out on the drainage system on your site. Sometimes you can find that while your waste pipes can drain to the rear, there may be a connecting line which may drain under your house and discharge to a main sewer at the front. In this instance, making a connection to the front maybe be straightforward and in your own control provided the connection is made within your own boundary. – Aidan McDonald

Aidan McDonald is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland