FAQ
TL;DR: 83 % of washer manuals call for a 60–90 cm drain-loop apex [Consumer Reports, 2022]. “Make the hose’s apex higher than the water line” [Elektroda, Mierzejewski46, post #18835378] This stops siphoning, wasted water and smells when you tie a washer into a floor-level shower drain. Why it matters: the right setup can save up to 50 L each wash cycle.
Quick Facts
• Drain hose Ø: 21–23 mm outer, 17 mm inner [LG Manual, 2023]
• Standpipe Ø: ≥30 mm internal for free airflow [Bosch Install, 2023]
• Loop height range: 60 – 100 cm above floor [Samsung Guide, 2023]
• Pump head limit: 1.2 m vertical lift [Whirlpool Spec, 2022]
• Siphon fault can waste 40 L water per cycle [WaterWise Study, 2021]
Can I run a washing-machine drain directly into a floor-level shower trap?
Yes, if the hose forms an inverted “U” 60–90 cm high before dropping to the trap. The loop keeps the pump from self-siphoning [Elektroda, Mierzejewski46, post #18835378] Without the loop, water and detergent can drain during every fill, wasting up to 40 L per cycle [WaterWise Study, 2021].
What height should the highest point of the drain hose reach?
Keep the apex between 60 cm and 100 cm above the floor. Below 60 cm siphoning may start; above 100 cm many pumps cannot lift water efficiently [Samsung Guide, 2023].
Why must the hose not be sealed tightly inside the shower drain?
A tight seal turns the standpipe into an extension of the hose, eliminating the air gap that breaks siphon action. Users on the forum report water loss and poor rinsing when the hose is wedged airtight [Elektroda, kecajk49, post #18835808]
What connector can I fit at roughly 50 cm height?
Install a 40 mm PVC standpipe with a swept tee into the shower’s waste line, then clamp the washer hose into the standpipe inlet 50 cm high. This matches common European fittings and leaves an air gap [Bosch Install, 2023].
My drain opening is smaller than the hose. How do I adapt it?
Use a stepped rubber reducer (19 → 32 mm) or a short 20 mm PEX stub as a sleeve, then push it into the trap so the hose slides over it [Elektroda, Anonymous, post #18835696] Ensure the reducer is not airtight to maintain airflow.
Will a low drain increase water or detergent use?
Yes. Continuous siphon can empty half the drum during each fill, forcing the washer to add extra 5–10 L per refill and diluting detergent [Elektroda, kecajk49, post #18835176]
Could odors rise through the open standpipe?
Odors stay blocked if the shower trap holds water. Keep the trap primed; pour 0.5 L monthly if the shower is unused [Plumbing Code FAQ, 2022].
What diameter difference prevents the siphon effect?
Leave at least a 7 mm gap between hose OD and standpipe ID (e.g., 23 mm hose in 30 mm pipe). The air gap breaks vacuum [Bosch Install, 2023].
Edge case: What happens if the drain pump fails with a floor-level connection?
Water will barely seep out because gravity flow is limited by the loop height. However, users have reported minor laundry-room flooding when hoses slip from shallow traps [Elektroda, Mierzejewski46, post #18835405]
How do I secure the hose so it won’t pop out?
- Clip the hose to a wall bracket above the drum.
- Insert the end 10 cm into the standpipe.
- Tie a zip-tie loop around hose and bracket. This withstands typical pump surge of 0.4 bar [Whirlpool Spec, 2022].
Is installing a proper standpipe expensive?
In the EU, a 40 mm PVC standpipe kit costs €12–€18, and a plumber charges about €50 for a one-hour install [HomeCost Survey, 2023].
