Is a backflow valve required for insurance cover in Germany?
In short
Is a backflow valve required for insurance cover in Germany? Not by law, but by your policy: the model conditions say backflow protection in rooms at risk must be kept working. If it is missing through gross negligence, the insurer may reduce payment, with intent refuse it. If a valve would not have prevented the loss, you are paid in full. Retrofitting often costs EUR 1,500 to 2,500.
What backflow protection costs in Germany, from published tradesman prices.
Example
Typical range
Simple backflow valve, material only
about EUR 95 to 200
Seals and small parts
about EUR 50 to 100
Installation by a specialist firm, labour only
about EUR 500 to 800
Retrofit including installation, typical case
about EUR 1,500 to 2,500
Guide values as of October 2026 from published cost examples.
The reduction rates in the worked example are assumptions;
how much is cut depends on the individual case.
Worked example
Thunderstorm, sewer overflows, EUR 30,000 damage in the basement
Sewage pushes up through the floor drain into the converted basement. The contract contains the safety rule on backflow protection.
Damage to screed, walls, heating
EUR 30,000
Valve installed and serviced every year
full payment
Valve present, not serviced for years, assumed 30 percent cut
EUR 21,000
No valve despite the contract, assumed 60 percent cut
EUR 12,000
A valve for around EUR 2,000 and a service record decide on up to EUR 18,000 here. The reduction rates are assumptions; in a dispute the courts set them.
The duty is in the contract, not in the law
Whether you need a backflow valve (Rückstauklappe) for the insurer to pay is not set by statute but by your contract. The insurers' model conditions for buildings insurance list it as a safety rule: backflow protection in rooms at risk must be kept working and drainage pipes on the property must be kept clear.
Rooms at risk are those with drains below the backflow level, typically basements with a floor drain, washing machine, shower or toilet. Sewage backflow itself is only covered by the natural hazards add-on (Elementarschadenversicherung), and only if heavy rain or flooding caused it. Whether your municipality also requires backflow protection in its drainage statutes, your local wastewater utility can tell you.
What happens if the valve is missing or stuck
If the backflow protection is missing or does not work, you have breached a contractual duty. Section 28 VVG sets out the consequences. Two questions decide: how serious is your fault, and did the missing valve actually cause the damage?
Situation
Effect on payment
Valve deliberately removed or kept open
intent: insurer need not pay
Valve never installed although the contract requires it and you knew
can be gross negligence: reduction by degree of fault
Valve clogged after years without maintenance
reduction possible, depending on fault
Valve maintained but fails anyway
no fault: full payment
Water came in through a basement window, not the sewer
valve not causal: full payment (section 28(3) VVG)
Gross negligence: the burden is on you
With gross negligence the insurer may cut its payment in proportion to how serious your fault was. The burden of proof is unusual: you must show that you were not grossly negligent, not the insurer that you were (section 28(2) VVG).
That is why records matter. An installation invoice, maintenance records and photos help you far more in a dispute than any explanation afterwards. After an intentional or grossly negligent breach the insurer may also cancel the contract within one month.
When the missing valve does not matter
The insurer must still pay to the extent the breach did not cause the loss or affect its size (section 28(3) VVG). If rainwater runs down the basement stairs or through a light well, even the best valve would not have helped.
This does not apply if you deceive the insurer. And it only helps for the part of the loss that arose independently of the valve.
When you do not need a backflow valve
If all drains, toilets and showers are above the backflow level, there is no room at risk. The safety rule does not apply and a valve would be pointless. That is the case for many houses without a basement or with a dry basement.
As a tenant you do not have to install the valve, that is the owner's job. If you live in a basement flat with natural hazard cover on your contents insurance, still ask your landlord about installation and maintenance.
Step by step
Find all drains, toilets and showers in the basement that lie below street level.
Check in your contract whether backflow is covered and which safety rules apply.
Have missing protection fitted by a specialist firm and keep the invoice.
Schedule maintenance as the manufacturer recommends and keep proof.
After converting the basement, review contract and protection again.
Checklist
Natural hazards add-on including backflow
Backflow protection on every drain below the backflow level
Installation invoice filed
Maintenance records for recent years at hand
Drainage pipes on the property clear
Common mistakes
Not closing a manually operated valve when heavy rain is forecast
Installing the valve and never servicing it
Assuming there is no money without a valve and not reporting the loss
Accepting a cut without checking whether the valve was causal at all
Questions and answers
Frequently asked
Does the insurer pay nothing if the backflow valve is missing?
Not automatically.
With simple negligence it pays in full, with gross negligence it reduces,
only intent removes cover entirely.
Do I have to prove I was not grossly negligent?
Yes, under section 28(2) VVG that burden is on you.
Records of installation and servicing are therefore important.
Does the duty also apply to contents insurance?
If your contents policy covers backflow through a natural hazards add-on,
similar safety rules may apply.
Read your conditions.
Is a valve enough for a basement toilet?
That depends on the installation.
A specialist decides which protection fits;
for toilets below the backflow level it is often a lifting unit.
What if the previous owner removed the valve?
Check all basement drains after buying.
Not knowing speaks against gross negligence but does not replace fitting one.
