A neighbour removed some window bars using an angle grinder and it has left nasty scars on the surrounding stonework where he overshot while grinding. I don't know if that was due to lack of experience with the angle grinder, or not.
In your case, if you're careful then any accidental contact...
There are various brands of small cube-shaped lasers that cost about £50. Example: I have a Bosch Quigo. Then the prices jump substantially. I guess the more expensive ones are better, but I've never used one.
Looking at your video, I think his castors may be ready-made dollys and he's chosen the width of the pool to suit them. Something vaguely like this:
https://www.screwfix.com/p/hilka-pro-craft-400kg-wheel-dollies-2-pack/77671
I guess it's not the castors per se that are my concern - as you say, you can buy some pretty sturdy ones - but rather the fact that once it's on castors the rest of the base is unsupported. So the OSB (or whatever) base is no longer just firmly sandwiched between the water and the ground, but...
You need battens or something around the top edge to resist the sides bowing outwards. Fix them solidly at the corners.
390 kg on castors sounds like quite a challenge.
Fine. Just paint it with whatever you're painting the surrounding woodwork with. But do wait until it's hardened.
What do the experts think? Maybe there is something you can use sooner, if you don't want to look at unpainted putty?
Yes.
Air is getting into the system somehow. Others will have suggestions about what's the most likely cause.
Is it a sealed system, or is there a header tank?
A "slight thumping" is nothing to worry about.
Bad water hammer sounds like the pipes are about to shake themselves apart, with enough vibration for things to fall off shelves, after waking up everyone within half a mile.
I witnessed one when I was a student. The landlord had upgraded the shower over the summer; one of the flatmates was using the shower for the first time and the rest of us smelt a burning plastic smell from the cupboard under the stairs. On opening the cupboard door, we saw a molten plastic CU...
For me it's the end time that matters. I load the washing machine late at night, guess what time I'm going to get up in the morning, and set the delay so that the machine finishes at around that time. When I get up, I hang the washing outside. I don't want it to run earlier than necessary as the...