Water Tank Washing Experience oh Water Tank Washing Experience

My water tank washing experience turn to become nightmare.

I install a water filter (RM 399 Aquoco, FRP 10x44), so I ask the guy to clean the water tank together. ( RM 100 only cheap cheap).

But he accidentally step on my tank and it crack.

Can not blame him, the developer didn't clean the surface properly when install the water tank, a lot of small stone underneath the water tank.

My ceiling is wet and leaking down from the master bedroom.

Damn kanasai.

So I ask my plumber come check, all connection OK, he say most probably is tank crack.

Need 1.7 k to install new tank.

My model:

Kossan N250RAA PE Water Tank Round Series 1420MM (T) x 1140MM (B) 300G (NC)

https://www.ewarehouse.my/plumbing/hdpe-water-tank/Kossan-N250RAA-PE-Water-Tank-Round-Series-1420MM-T-x-1140MM-B-300G-NC-ries-1420mm-t-x-1140mm-b-300g-nc?sort=p.date_added&order=DESC&limit=100

Description

Effective Capacity (EC): 250G.
Nominal Capacity (NC): 300G.
Top Diameter (T): 1420mm .
Bottom Diameter (B): 1140mm .
Diameter Height w/o cover: 990mm .
Diameter Height c/w cover: 1115mm .

Kossan N250RA PE Water Tank Round Series 1500MM (T) x 1219MM (B) 300G (NC)

https://www.ewarehouse.my/Kossan-N250RA-PE-Water-Tank-Round-Series-1500MM-T-x-1219MM-B-300G-NC-k?search=kossan%20n250

How I temporarily solve the problem:

1) The Filter guy help me fill the crack. ( not sure can last how long)

2) Now temporarily no leakage from ceiling.

3) But now got overflow problem.

4) Change the Float Valve. ( RM 25, workmanship RM 50 )

5) But still overflow problem, so HOW???

6) Suspect is backflow problem.... Need to install CHECK VALVE. I have been using the bypass filter for 10 years, now only have back flow problem, really don't understand...