Underwater pressure washing

[jimwill]

Hi everyone! I wasn't able to maintain my pool for a while, and I have black algae spots on the bottom, attached to calcium buildup / scale. I can remove them with a small stiff wire brush, but it's time-consuming because I have to weigh myself down to the bottom and scrub each spot.

I've seen older threads about pressure washing underwater. Has anyone had success doing this? If so, what type of pressure washer and nozzle should I use to do this safely without damaging my pool? I've seen scuba divers doing this, so I guess it can't be done from the deck with a long wand.

Any advice and shared experience is appreciated!

Thanks,
Jim

 

[mknauss]

I believe @Katodude is the user of that method ---

 

[PoolStored]

Get a weak pressure washer and get into the pool and start pressure washing it. The algae should pop off. Be VERY careful not to damage your plaster (hence the weak pressure washer). Larger tip angles will have less pressure.

Then get a 1 gallon pump spray. Fill it with the strongest LC you can find. Get in the pool and spray those sections.

Keep your FC at 20% of your CYA for a couple weeks.

 

[jimwill]

Get a weak pressure washer and get into the pool and start pressure washing it. The algae should pop off. Be VERY careful not to damage your plaster (hence the weak pressure washer). Larger tip angles will have less pressure.

Then get a 1 gallon pump spray. Fill it with the strongest LC you can find. Get in the pool and spray those sections.

Keep your FC at 20% of your CYA for a couple weeks.

What PSI do you recommend and what tip angle?

 

[Katodude]

Something like a 2500 psi with a 15 degree nozzle. Or 3000 PSI with a 25 degree nozzle. Also distance from the plaster matters a lot. Get close enough to pop off the algae but not close enough to damage the plaster.

Also will depend on the age and condition of your plaster. In any case this method seems to be less aggressive than a wire brush.

Use common sense and be careful.

Dosing those sections with chlorine after is also very important. Black algae has roots and you are trying to kill those roots.

The bad news is you will now be susceptible to black algae for as long as you have your pool. You will need to live at the high end of the CYA/FC table forever.