Frequently asked questions – Basement waterproofing (FAQs)

Click the questions below to reveal the answer.

Are all DELTA and Koster products stock items and how long does it take for delivery?

Almost all of the DELTA and Koster range is available on a next working day delivery (Mon-Fri) if you order before 2:30pm (early deliveries available at an additional cost).

are all delta and koster products stock items and how long does it take for delivery?

As a pump station is an essential part of a cavity drainage system designed to prevent ground water from damaging a Basement, what emergency provisions are recommended?

The sump must be provided with duplicate pumps together with UPS (uninterruptible power supply), usually consisting of an automatically trickle charged battery system. A high water level alarm is also essential, and if the property is frequently left unattended for long periods, then it would be wise to include a Telemax SMS messaging system for remote warning.

Please note that remote warning should also be considered for rainwater and surface water applications.

as a pump station is an essential part of a cavity drainage system designed to prevent ground water from damaging a basement, what emergency provisions are recommended?

Can pump stations be used for rainwater applications?

Small sheltered catchment areas up to 12m² (such as Lightwells or Stairwells) can normally be served by the same pump station that serves the cavity drainage system. For larger or more exposed catchment areas separate pump stations are advisable, and it is also important to ensure that adequate provision has been included to prevent internal flooding of the building in the event of a 24hr disruption, e.g. power failure. We will be pleased to provide further guidance if required.

can pump stations be used for rainwater applications?

Can we make a sump chamber ourselves out of concrete rings?

The answer is yes but this is a risky strategy as you will be de-watering below the top of slab level as water enters into the chamber through the ring interfaces. Call us on 01992523523 and ask for our pump department for further advise.

can we make a sump chamber ourselves out of concrete rings?

Can you mix Groundwater/Surface Water with Foul and Grey Water Sump Pump Systems?

No, we advise to keep these systems separate for the following reasons:

Blockages – if the Foul Sump blocks due to liquid fats and/or foreign bodies (wet wipes, nappies etc.) you can stop using the basement toilet and kitchen facilities and there is no immediate emergency and there should be no damage caused. The Groundwater/Surface water sump needs to be operational at all times otherwise if the mixed system blocks the build up of water behind the membrane system can back up into your basement causing significant damage which could be very expensive to rectify.

Foul smells – if a mixed system the smells from the foul system can travel back behind the membrane which can enter the residential parts of the basement.

Larger chamber – Deeper excavations especially in basements where there are water table problems can be more problematic and costly. It is often more economical to install two smaller separate chambers as opposed to one large chamber.

can you mix groundwater/surface water with foul and grey water sump pump systems?

Do I Need Ventilation?

Heating and Ventilation: The environment in basements should be controlled by having balanced heating and ventilation to combat the small risk of condensation. All habitable rooms, kitchens, utility rooms, sanitary accommodation and bathrooms located within the basement, should follow the ventilation provisions of the Building Regulations 2000 part F1.

do i need ventilation?

How to waterproof a basement / cellar?

To waterproof your basement with the DELTA system there are two main components.

1. Cavity drain membranes (dimpled/studded plastic sheets) which wrap the walls and floors to keep your finished wall dry.

2. Drainage & sump pumps to drain the collected water to an existing drainage system, manhole or soak away.

The cavity drain membranes are fixed to the wall with our various fixing plugs and sealed together with our butyl rubber tapes.

For a professional job with guarantees we recommend using one of our registered installers  – click here to request some installers that cover your area.

For a quick demonstration on how the membrane system is put together view our installation guide here.

how to waterproof a basement / cellar?

If it’s feasible for a basement or lower ground floor area to discharge by gravity drain to the sewer, is this acceptable?

If the floor level is below street level and contains habitable rooms then it is usually considered sensible to incorporate a sump station. The pumped main should be arranged to form a back flow loop so that it is higher than the flood level. If the flood level is unknown, we normally recommend the invert of the loop is at least 300mm above the surface of the adjacent road. This will provide the best flood protection in the event that the sewer becomes surcharged (full and pressurised).

Please note that anti-flooding valves should only be used for flood protection when the rooms are of minimal importance and the occupants have access to other sanitary appliances above street level that do not discharge via the anti-flooding valve.

if it’s feasible for a basement or lower ground floor area to discharge by gravity drain to the sewer, is this acceptable?

My Architect has recommended your system, how do I get the system installed?

DELTA® have a nationwide network of registered installers. Please call 01992523523 or ‘get in touch‘ and we will be happy to give you information on local contractors.

my architect has recommended your system, how do i get the system installed?

Should we consider external waterproofing in addition to the Internal?

Where possible this is always recommended as the building is the first line of resistance and every attempt should be made thus reducing the work the internal sump is required to do.

should we consider external waterproofing in addition to the internal?

What are the acceptable levels allowed for ponding when using your DELTA® MS20 system on a concrete floor?

See section 15.2 of our BBA certificates;
The concrete base must have a surface regularity with a maximum permissible departure of 
5 mm from the underside of a 2 m straight edge, resting in contact with the floor, in accordance with BS 8204-1: 2003.

After carrying out a flood test to determine any depressions, and falls, they should be made good in accordance with Clause 15.4 . In any event ponding should be avoided.

what are the acceptable levels allowed for ponding when using your delta® ms20 system on a concrete floor?

What are the sump chambers made from?

Virgin HDPE tested to ISO 14/15 so they are pressure resistant and spun bonded so there are no joins on the chambers.

what are the sump chambers made from?

What is the difference between structural waterproofing and damp proofing?

Structural waterproofing deals with a range of  below ground problems for example basements/cellars, underground vaults, tunnels, car park decks etc. Any structure that has retaining walls (walls that have soil behind them).

Damp proofing deals with problems at ground level and above.

what is the difference between structural waterproofing and damp proofing?

What is the difference between the MS500 and DELTA® PT?

The DELTA® PT has a thermicaly bonded mesh which provides a key for either directly applied plaster or a dot and dab thermal or plasterboard. The MS500 is designed to have dry lining in front of it, either independent or timber battens screwed into the Delta plugs.

what is the difference between the ms500 and delta® pt?

What is the MS500 and MS20 made from?

Virgin High density Polyethylene, it is not recycled but recyclable. Beware some similar looking products imported by other as these are often made from Polypropylene and can get brittle and crack below 5 degrees.

what is the ms500 and ms20 made from?

What is the power supply required for the sump?

13 amp non switchable spur, ideally not off the basement ring main.

what is the power supply required for the sump?

What is the stud depth of the MS500 and MS20?

8 and 20mm

what is the stud depth of the ms500 and ms20?

What product can i use to waterproof a lightwell?

You can use our Delta PT-Lath meshed membrane to waterproof a lightwell. See this case study as an example.

what product can i use to waterproof a lightwell?

When planning a foul water pump station for a dwelling, should emergency storage be included?

If all the sanitary appliances in a dwelling are reliant on the pump station, then Building Regulations ADH advises that 150L/person emergency storage should be provided. This is designed to ensure that the sanitary appliances remain functional for a 24hr period in the event of a disruption. If the anticipated water consumption is less than 150L/person because the sanitary appliances have been selected to comply with Building Regulation 17K or the Code of Sustainable Homes, then (subject to Building Control agreement) the emergency storage could be reduced as appropriate. If only part of the dwelling is located below street level, and there are a sufficient number of appliances (based on BS 6465) on upper floors that discharge to the sewer by gravity, then (subject to Building Control agreement) it may be reasonable to consider that emergency storage is NOT essential for the pump station, because the users have sufficient alternative sanitary appliances.

Please note that for ‘high end’ projects, the client’s Project Administrator may wish to consider that emergency storage should be provided to minimise any inconvenience during a disruption (e.g. power failure).

when planning a foul water pump station for a dwelling, should emergency storage be included?

Why do I need a Sump & Pump?

To comply to the British standard we usually recommend that a pump system be installed as part of the system. A Sump Pump manages the water build up from the internal cavity membrane system equalizing the water pressure by discharging it to a more suitable outlet.

why do i need a sump & pump?

Why does the ground and foul water need to be collected and pumped separately?

Mainly because any gases from the foul system could travel back up through to the cavity membrane system and cause the basement rooms to smell, these gases could also become dangerous/explosive.

Also the same applies to foul waste water backing up into the system because of back pressure from the main drains.

why does the ground and foul water need to be collected and pumped separately?

Why should you buy the products from DELTA®?

Because you will get expert advice by what we believe to be the most qualified individuals in the industry and onsite support second to none.

why should you buy the products from delta®?

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