What's the safety recommendation/equipment for underground water tank that is built next to underground pump room for flood protection? what safety systems to be used inside pump room and tank?Thanks. Please provide standards e.x or general items in one system like level sensor and actuators, submersible pumps water pit inside room, if any safety dimensions to be undertaken. and so on..

The most commonly applied protection is to construct the access to the pumping station and the tank above the flood elevation. It may be a large amount of site work, but it is the best protection. Also two means of access/egress. These are physical plant protections, not instrument protections.

Provide level switch operated drainage pump in pump room.

Amer, is your main concern the below grade flooding? Not from flood waters?

All of the above. Possibly locate the majority of the electrical appurtenances on a structure outside the underground vault. Minimize losses if flooding would happen.

Tanks, Gary, Kurt & Sinnadurai

Kurt ,our concern is flood resulting from overflow water from tank to pump room.

That was my impression but needed to ask.

Drainage, sump pumps, alarms. Anything along those lines would help protect your pumping equipment.

You should have large capacity drainage pumps with level sensors to drain out water from the pump room.

MY suggestion is 2 - fold.
* the floor design of your pumping room should be such that the level of the drain pump should be lower the that of your main pump.

This way any flooding will gather below the main pump and the drain pump will be activated by flood sensor before the flood water reaches the main pump level.

2) Select an over-hung type for your main pump thus having all electrical works outside the pumping room. The limitation on this is a 4 meter depth mark line for the this type of pump .

I have previously used dry mounted submersibles in this setup. all control gear above flood zone you still require drainage pumps in case of flooding, however with using dry mounted submersibles as the main pumps they will still operate in the case of a flood event.
I would still use high level alarms to warn of a flood event but the risk to equipment is minimised.

I agree with Gary that the installation dead volume should exceed tank volumes up to the positioning of the pumps. This should prevent even a tank breakage. Of course as Andrew points out, submersibles are an excellent option and don't require this extra space.

But They don't dismiss you from installing drainage pumps, as if pumps begin to discharge the tanks in a flooded room, tanks can float and you'll be in a great mess.

To prevent exceeding input level in tanks, I prefer solenoid (NC) valves electrically driven over mechanical shut off systems, install them even if float switches command the pumps that fill the tanks, simply close the input too by means of another float switch (safe redundancy system).

To design a good drainage system my basics are: two pumps, two independent discharge pipes (don't trust on non return valves for this type of parallel installation, just avoid paralell, go independent drainage). Get them work one minute every two days or so by an automatic system, (anticlog guarranteed) and size each of them for full capacity (redundancy). By means of a higher level float you will have the second pump working in case the first fails. You can also alternate the principal and the secondary in a time basis. Each time you alternate you make it work a minute.

The common scenario is clogged pumps due to years in stand-by mode waiting for an event that may never happen.

By installing the Dry wel submersibles, you are covered from flooding damage to the pumping equipment, and can operate during those conditions. A drainage pump is still recommended to clear the pump room to allow for access to address the cause or inspect the equipment. As Sergio explained on the alternating operation of duty pump has proven reliability of the pumping system, although I prefer alternating the duty pump instead of running it at short intervals to ensure smooth operation. Alternatively a sump can be created and submersibles can be installed, a coast calculation should be done to validated such an system.