Wet risers

[AnthonyB]

Building of 70.1 metres high & 17 floors has a dry riser. Guidance says that it should be wet (>60m).

Inlet is a 4 way inlet with 4 x 2.5" lines feeding into the single main that has two 2.5" outlets at each landing.

Can modern pumps sustain this main with this set up & if not what's the solution

[kurnal]

fireground approximations would say that at 60m to give a working pressure of 5.5 bars at the branch we would need about 12 Bars at the pump. The pump will be capable of deliving this but it will be beyond its duty point towards the maxiomum limit.Available flow at this pressure will be very low.  At 70m this becomes 13 Bars- and the pump performance curve will be falling off steeply. I think the biggest weakness though is the hose connecting the pump to the dry main which will have a SWP of 10Bar and if new will be ok to 15Bar tops.

To deliver this with any reliability at all we would need a good pressure in the towns mains feeding the pump - with the pump working its rocks off the smallest problem or pressure drop at the ground level- eg due to hose kinks, collapse of soft suction or pressure variations in the incoming supply will be hugely magnified at high levels in the building and  may cause total failure of the fire fighing jet on which the crew are relying.

As for answers heres a selection some wacky and impractical but here goes
Domestic sprinklers on the upper floors if a residential building may be one solution,

or specific hose on site tested to say 20Bar for the fire service use together with a check on the towns mains pressure at peak times. If supplies are poor a 15 cubic meter minimum  static tank first floor or second floor level with a hard suction  outlet at ground floor level  level to assist the pump ?

[Midland Retty]

New guidance dictates that builings taller than 50 metres now need wet rising mains due to pressures required for modern tactical firefighting procedures.

Aside from sprinklers the alternative Kurnal mentioned would be wholly unpracticable.

Also remember that sprinklers don't guarantee a fire will be totally extinguished, it just means the fire should be controlled, so you still need a supply of water for fire crews to use.  Plus crews should not committ into any building unless they have a safety jet on hand.

Is the height you have quoted to the top floor or top of the building? If it is the top floor it begs the question why the building wasnt fitted with a wet riser at the construction stage, then again your storey height isn't going to be 10 metres so it seems to me that this should have been a wet riser from the word go.

Is there any history about this? do we know why a wet riser wasn't fitted in the first place ?

The solution I'm afraid as I see it is that a wet riser will need to be installed beyond any shadow of a doubt. There are no viable or practical alternatives.

Whatever you do please please contact the local  fire service straight away about the situation - they may need to augment their pre determined attendance to the tower block, they may need to look at sending additional resources to each call out and decide how they will tackle low pressure water scenarios.

There are no alternatives, and it is in the blocks owners interests to get this done, to protect residents and of course to protect the material construction of the block itself.

 

[AnthonyB]

1972-4 build, dry main from beginning, no history available.

70.1m is thought the overall height of the tower from ground, but it isn't clear if that includes the smaller plant level on the roof tower - this would drop the height to the top of the 17th floor down to 64/65m, although the top landing valve is on the lower level of this plant area.

There are no test records & a riser testing company had to abort without looking at the installation as they didn't have water board permission to break into a main to test it (must have been a pump in a van rather than an old fire engine).

Fingers crossed that it is actually a wet with the inlet being for boost purposes, but there is nothing to state if this is the fact and the building management that have been there 20-odd years swear it's dry.

It had a fire in recent years, but it was localised and the main not charged - no issue raised by local crews.

Also it runs single stage evac despite only 2 x 1metre stairs and quite large potential floor occupancies, but thats another matter!

[kurnal]

Aside from sprinklers the alternative Kurnal mentioned would be wholly unpracticable.

The solution I'm afraid as I see it is that a wet riser will need to be installed beyond any shadow of a doubt. There are no viable or practical alternatives.

Just trying to think outside the box. A tank at lower levels may have been more practicable than a tank at the top!

But with Anthonys follow up it sounds like it may have just crept in at the time of construction- if I recall for flats (without checking) its the height to the top floor,I think small storeys housing plant rooms only  can be discounted  and the relevant height for wet risers  was  60m but I cant remember without checking. There were requirements for automatic booster pumps and tanks.  (may dig out the old CP3s  later).

Anthony if you PM me if its flats I may be able to help further with this.

The other thing is that if permission is needed to break into the main to test,  it it sounds like it might be a wet riser fed by towns mains to me.But surely theres no way this could have ever worked without pumps . Bet the water quality people would have a field day with that today.

[Clevelandfire 3]

Yes the old standard dictated 60 metres as already stated. Kurnal lets be realistic. Sprinklers wouldn't solve the problem and besides the cost to install a system on that scale would probably surpass a wet riser conversion anyway. You still need water for firefighting purposes regardless of sprinkies. And where exactly are you going to put a tank in the middle of a tower block?. If you have owner occupiers in the block how are you going to try and go about getting them to pay for sprinklers to be added within their flat, what do you do if they wont play ball. Service & maintenance would be a nightmare.

This is serious stuff. You can not mess around when it comes to tower blocks.
 The owners are going to have to adapt to technical change. The world has changed since tower blocks were first built.Double glazing enhances the chance of backdrafts. Whoever owns the block will find themselves up pooey creek if there is a fire there because to be quite frank there aint much the fire service can do if they aint got adequate water supplies. Kurnal you should be well aware of that given your background.

If someone dies in that block as a result of crews having sufficient water to stop fire spreading or affect a rescue then the brown smelly stuff will hit the fan at lightning speed. As Retty says you had better inform the fire service of this like yesterday because if the what happened in London and Southampton dont demonstrate what happens when things go horribly wrong I dont know whatdoesl. The fire service need to know what they've got to play with. Never mind that there was an incident way back and the fire service didnt pick up on any problems. The fact is as you said yourself AB they didnt nee d to use the riser so its no suprise nothing was said.  The responsibility is on the landlord not the fire service. And who was testing this riser?There must have bene previous testing . Please tell me it was subjected to annual testing. Has the contractor not made comment about the inadequacy of the installation?

[kurnal]

Well actually  I dont disagree with any of what you say C3.
However we are not sure that a wet riser is required though following the posters second clarification, and if it turms out that its only a matter of 65m instead of 60 then a retrospective  wet riser installation for the sake of one or two  floors in a building that has been standing without one for 40 years may also be excessive. Domestic sprinklers in the topmost floors where the dry riser is beyond normal limits may be a reasonable compromise to make the place safer than it has been in the past and reduce the overall level of risk.

My other  off the wall suggestion was just to get people thinking. Wet risers also need tanks, dual pumps etc and no solution of this nature is going to be cheap or easy.

Theres a lot of buildings  with problems like this.

[Midland Retty]

I think if you can get up to 5 bar on all landings then that might be ok, the modern branches used for gas cooling need  a minimum of 5 or 5.5 bars to be effective.

But as we  have already discussed I would be very suprised if you get that, infact I can say with certainty that you won't.

Whilst it would seem excessive to insist that a wet riser is should be installed, we mustn't use the excuse that just because something has been like that for 40 years we can live with it, not when it comes to something like a high rise block.

I accept doemstic sprinklers could play their part, but I can only ever see them being an interim measure.





 

[AnthonyB]

By the way - should have said that it's an office block with pubs/clubs to ground/basement.

It should have been tested each year, but never has and the one time it was to be the testing company decided not to go ahead as they hadn't got the permission to breach a hydrant - so they didn't even look at it. it's clear it's not really been looked at as the brass inlets have gone green!

[Midland Retty]

Ah now he tells us! (Our fault for assuming you were talking about a high rise tower block).

This puts a slightly different slant on things, because, one presumes, there is no sleeping risk within the premises.

Still probably needs a wet riser for firefighting purposes but clearly if people are awake and alert (apart from the nightclub) and can evacuate the property fairly quickly then its not as perhaps serious as we first thought.

Long term for the benefit of fire crews and building protection you will still need to look at a permanent solution. Again sprinklers may be ok, but you still need to give fire crews something to squirt at a reasonable pressure.

So basically the solution is still the same, but maybe timescales can be relaxed a little in which to get something sorted, in the meantime the management of the building needs to be on its toes, and staff, visitors made aware that if there is a fire alarm activation they must treat it seriously and evacuate straight away.

And of course you still need to talk to the fire service about these issues, it is in everyone's interest!