We have a warehouse used for paper (2.5ton reels) which is over 20,000msq.  Approximately 40,000msq to be fair!  Originally built 30(ish) years ago.  Had (past tense) a sprinkler system fitted.

Problems occurred when sprinkler pipes began to leak, causing damage to paper stock.  Resulted in customer complaints, so the then owners decided to disconnect the sprinkler system...avoids paper getting damaged and saved maintenance costs of sprinkler system. ?

As the building originally had a sprinkler system, must the Responsible Person (new owner) reinstate the sprinkler?  I can see Building Regulations guidance gives 20,000msq as the threshold for new buildings, plus guidance for sprinklers recommends that warehouses over 20,000msq have sprinklers, but unless it is mandatory, the client will not do it.  The Fire Risk Assessment seems a bit unclear and says that it is recommended the sprinkler system be reinstated...

Any guidance / experience / help much appreciated here! 

Yes, as that requirement was in existence at the time of build and unless you have insurance and building control approval for the effective removal of the system you are in sticky water before even considering the Fire Safety Order!

If you split it into compartments that are below the threshold you may be OK - this is common in former large open single occupancy warehouses that are subsequently sub divided for multi occupancy - as the building work creates compartments below the threshold Building Control does not require the sprinklers and the insurers usually likewise.

It sounds like the system has been neglected previously!

Hi AnthonyB, thank you very much as always.  That's really helpful with our discussions with the client.