Sink Waste Fittings Explained

Article by Peter Smith - Caravans Plus

Read Time: 3 mins

We have three styles of waste fittings and they are not interchangeable. Check the hole size in your sink or basin before ordering, then match it to the correct waste fitting style.

1. Quick Size Guide

Sink or basin hole	Waste fitting style	Notes
35mm	Standard 25mm waste	Straight or angled waste. Plug is normally purchased separately.
40mm	SMEV waste	Includes grate and plug. Usually used with SMEV sinks.
45mm	90 degree waste	Includes grate and plug. Available with a 90 degree bend.
50mm	Household waste	Normally sourced from a hardware store, not suitable for most predrilled stainless caravan sinks.

If your hole is close to one of these sizes, measure the actual cut-out and compare it with the product details before ordering. A comment on this guide notes a 40mm right-angle waste fitting was used successfully in a 38mm hole, but you should still check the fitting and your sink before relying on that.

2. Standard 25mm Waste, Suit 35mm Hole

One type is the 25mm waste - straight or angle. The 25mm plug must be purchased separately. These are defined for each sink or basin that uses them. They are made of two sections - one piece fits from the top and requires a small smear of silicone under the lip to prevent leaks. The bottom section screws, by hand, from underneath.

We suggest the 25mm PVC black hose makes an ideal internal drain hose as it is the best fit over waste fittings. While we do sell the corrugated 25mm hose it is quite difficult to fit the 25mm barbs. It doesn't matter if it curves up and down before exiting the floor, as it can act as an S-Trap to prevent foul air rising up the pipe, but don't allow any kinks.

Access to remove and unblock should be provided. Use a suitable hose clamp at the top. A simple 25mm PVC joiner can be used under the RV for connecting an additional length at the Caravan Park.

3. SMEV Waste, Suit 40mm Hole

SMEV sinks use a different waste size (at the time of writing a straight waste is included with every SMEV sink). These are fitted in a similar fashion to above, again to a 25mm ID hose, however they do not need silicone and they appear as all stainless when looking from above. They include the grate and plug.

4. 90 Degree Waste, Suit 45mm Hole

Part number: 042871

Some sinks use 45mm waste size. These are fitted in a similar fashion to above, again to a 25mm ID hose. These are only available with a 90 degree bend. They include the grate and plug.

5. Household Wastes, 50mm

We do not sell these as they are readily available from hardware stores. They may be appropriate for undrilled shower bases, however they will not fit into the predrilled holes in stainless steel sinks.