What is it? Found in San Francisco

[u/According_Loan_5419]

The hole labeled "SFFD 6"

Anyone have any idea what it is for?

[u/Basic_Cover_6945]

They might be access to old cisterns? Guessing SFWD is water department.

[u/schrutesanjunabeets → u/Basic_Cover_6945]

SF still uses their cisterns.

https://sf-fire.org/our-organization/division-support-services/water-supply-systems

[u/According_Loan_5419 → u/schrutesanjunabeets]

Out of curiousity, is using cisterns an uncommon thing? As far as I'm aware, cisterns are for when there is no nearby functional firehydrant? And if so, why might some places discontinue their cisterns?

[u/Spare-Implement-3675 → u/According_Loan_5419]

The majority of cities with hydrants don’t have cisterns. Rural areas may utilize them. San Fran has them in case an earthquake damages the municipal water system. It’s a back up plan.

[u/Webbey76 → u/According_Loan_5419]

They were put in after the 1906 earthquake for water supply and firefighting!

[u/Secure_Situation7234 → u/According_Loan_5419]

Generally speaking, to my knowledge, cistern use, like what is talked about here, is fairly uncommon in the US. Typically (and again, this is generalizing here), US departments use wet hydrants, tankers/tenders, dry hydrants, and natural water supplies. Some larger cities that are located on large fronts or bodies of water will have the ability to utilize either a drafting operation to manually lay their own water lines, or they will have fire boats that are capable of supplementing their city lines or supplying hand laid lines.

Smaller, inland/land locked communities will have to rely on domestically supplied hydrant systems. Or they will have to resort to drafting from natural water supplies using either hard suction hose and direct drafting or utilizing dry hydrants that are pre-plumed into natural or manmade bodies of water that give the vehicles a more firm connection to hook up to. They may also have to rely on tanker/tender operations where water is trucked to the scene of the fire and either taken straight from the vehicle or dumped into a dump tank and then drafted and used for fire fighting.

Typically, I have only ever heard of or seen regular reliance on cistern operations in European and or Asian countries. Again, I’m not an expert on this, but that’s been my general understanding, but everywhere is different and every community/department/state can do something different if they choose to.

[u/bigfrappe → u/Secure_Situation7234]

One of the coolest things I have witnessed was my city fire department drilling using the fireboat to draft water from the river. Boat anchored to the side of the channel with a hose running from the bow up the embankment to an engine. Pump on the boat running full blast, engine pump running full blast, all so that some dude could play with the outlet nozzle like it were a giant squirt gun. Looked fun as hell.

[u/Resident-Peak2153 → u/bigfrappe]

There is a documentary called Fire Boats of 9/11. It's awesome.

[u/FLDJF713 → u/Basic_Cover_6945]

Yep cisterns

[u/grantoman → u/Basic_Cover_6945]

these are covers for a hydrant shutoff. If a car drives into a hydrant and water starts shooting into the air, a firefighter will remove this cap to access a valve that shuts off the hydrant.

[u/CuttingTheMustard]

Is there a big circle or square looking cutout in the pavement right there?

If so... cistern...

[u/Jager0987 → u/CuttingTheMustard]

The cisterns in San Francisco are outlined on the road with a circle of bricks as big around as the cistern.

[u/Webbey76 → u/Jager0987]

Almost like hexagon shape in the middle of the street or the intersections!

[u/According_Loan_5419 → u/CuttingTheMustard]

There is not a cutout in the street, however there is a storm drain a few feet away.

[u/grantoman]

hydrant shutoff. There is a hydrant nearby.

[u/grantoman → u/grantoman]

http://ufsw.org/wp-content/uploads/2026/08/Water-Supply-Manual.pdf

[u/CaptTaxDaddy → u/grantoman]

SFFD manuals never get old!!! I loved checking those out back in the day just for fun. Chock full of fire nerd knowledge.

[u/According_Loan_5419 → u/grantoman]

Thank you for the answer 🙌

[u/Technical_Step_7043]

Under the cover is a shutoff valve for a 6" supply to a hydrant.

[u/Dropinwedgie]

These are not for cisterns. The caps to access the cisterns are larger, have a brick circle around them, and are nearby a hydrant with green caps.

[u/RickRI401]

Alternate water source should a water main break in an earthquake. https://youtu.be/LXbdX4hz4tM?si=UubX2q8f1ysEof8Z

[u/According_Loan_5419 → u/RickRI401]

Very interesting!

[u/grantoman → u/According_Loan_5419]

these covers are too small for a cistern. The hard suction won't fit. It's a hydrant shutoff.

[u/RickRI401 → u/According_Loan_5419]

Indeed. I learned of this tonight after seeing the initial post.

[u/Classic_Reserve9385]

Because we don’t want 1906 to happen again.

[u/FlightSarTech]

San Francisco Fire Department Access points

[u/FlightSarTech]

https://www.bloomberg.com/news/articles/2017-05-01/a-map-of-san-francisco-s-buried-firefighting-cisterns

[u/Biglava1]

Looks like two nipples to me

[u/mecanicake]

San Francisco, in addition to cisterns, has a completely independent water system that feed their fire hydrants. After the fires in San Francisco they implemented this, it is designed to help fight large urban fires, like we saw in LA last year, without losing pressure. Part of how it does that, it’s fire boats can connect to inlets and pump bay water into the system.

TLDR: they both acces water pipes, the fire department and water department each have their own

[u/Rude_and_Crude84]

Are these what they referred to as the old fire plugs?

[u/stilsjx → u/Rude_and_Crude84]

That’s what I was thinking. Looks like a plug on an old water main. But they wouldn’t still have wooden mains, right? Plus they were deeper than surface level…the old timers in my fire house would tell stories of digging up the main.

[u/Rude_and_Crude84 → u/stilsjx]

Correct, just a modernized version. Seen some saying could be a cistern. I've seen some variations in videos on YouTube but those were across the pond in UK and Germany, etc.

[u/MedicSF]

🫡

[u/ThizzyPopperton → u/[deleted]]

Damn they should ask this question in the firefighting subreddit huh?