Longshot, can anyone identify these covers

[Golden Triangle]

These covers are down the side of the house, can anyone help me identify what they are ? We are experiencing a bad case of centipedes, adult & babies, have killed I don't know how many babies today, had a fright in the shower yesterday, a 6 inch buggar hiding under the non slip mat, man that freaked me out, now have mothballs & Chaindrite powder everywhere. Thanks in advance 

The square one has water below, not sure if grey or foul

Edited July 10, 2021 by Golden Triangle
Extra info

[KannikaP]

Take the cover off and look down!

[Denim]

5 minutes ago, KannikaP said:

Take the cover off and look down!

 

Plus, turn on taps in kitchen and bathroom etc to see which tap goes with which cover.

[Crossy]

The round one is probably your septic tank.

 

Square one could be anything, grey water or whatever.

 

[LoliLoso]

The black round cover is the septic tank.

The rectangular concrete tiled cover is the drain.

[Golden Triangle]

Many thanks for the helpful replies, I'm not sure if the centipedes are breeding in the septic tank, is this  possible? If I have it cleaned out is there anything to put down there to stop the breeding centipedes?

[stubuzz]

The rectangular one is the grease trap.

[Artisi]

a can of good insect killing spray, sprayed down the hole will work wonders, just be prepared for a mass exodus of all sorts of creepy crawlies leaving at top speed ????

[Dr B]

As stated by a number of replies, the round lid looks like a septic tank and, if all has been plumbed correctly, the only way back into the house is through the WC trap. I do not know if centipedes can swim. The rectangular lid is the standard locally made, ill-fitting, cover to a grey water drain, into which all sorts of connections could be made. I have found, in Home Pro, numerous sinks and wastes which did not include a trap, which would allow insects to transit in either direction. Back in 2003 in Bangkok I managed to acquire a properly sealed drain cover, as shown on the attached photos. This is the ideal solution but it may no onger be available.

[carlyai]

10 hours ago, Dr B said:

As stated by a number of replies, the round lid looks like a septic tank and, if all has been plumbed correctly, the only way back into the house is through the WC trap. I do not know if centipedes can swim. The rectangular lid is the standard locally made, ill-fitting, cover to a grey water drain, into which all sorts of connections could be made. I have found, in Home Pro, numerous sinks and wastes which did not include a trap, which would allow insects to transit in either direction. Back in 2003 in Bangkok I managed to acquire a properly sealed drain cover, as shown on the attached photos. This is the ideal solution but it may no onger be available.

Very professional. Probably the only one that has been used for the job in Thailand.

[bbko]

In the past I also experienced an centipede infestation, finding at least 5 each day in the house, mostly at night. I did a two step approach to fix this problem, baking soda, then vinegar down the drains and more importantly find their breeding grounds in the garden.  Centipedes love dark wet environments, so I raked and cleaned all leaves, dead grass and debris, no more infestation.  

[topt]

On 7/10/2021 at 8:44 PM, Dr B said:

a properly sealed drain cover, as shown on the attached photos.

Just curious but how do you pry it open if you need to - I can't see any way to pull it up?

I have a couple of similar plastic covers (one on the septic and one on an underground tank) covered in tile but with built in handles - which on one have disintegrated in the sun over the years........  

[jojothai]

The round one really does look like a septic tank cover as stated by others. It looks like the air vent pipe to the top left.
I expect there should be screws under the two very small round circular caps in the cover.
If it is the septic tank be careful not to empty it unless you know if the ground water level is below the septic tank.
With all the recent rain the ground water level could be high. If so and you empty it, it could float upwards out of the ground. 
If that happens its a very hard job digging it out to get it rectified. 
Probably best to Try the killer spray first for the centipedes etc, into both covers for a time. See if it works.
Suggest that after that you try to take off the lids to see what condition the inside is in.

The rectangular cover may be difficult. Cannot see where the screws may be. Under the Tiles?

Edited July 11, 2021 by jojothai
add info

[Dr B]

On 7/11/2021 at 9:19 PM, topt said:

Just curious but how do you pry it open if you need to - I can't see any way to pull it up?

I have a couple of similar plastic covers (one on the septic and one on an underground tank) covered in tile but with built in handles - which on one have disintegrated in the sun over the years........  

When you undo the two allen screws it can be prised out easily with a screwdriver. It had a gasket seal and was a good but not a tight fit.