I doubt the landlords have any obligations. The only leverage you have is the fact the landlord will have to be bothered finding another tenant if he doesn't fix the water heater. 

There are horror stories, but for the landlord it's probably just making a phone call. I can only agree that if you go find a guy to fix it yourself, you might get ripped off, although I cannot imagine a water heater repair being that expensive, it is hardly high tech. Of course there might be the scenario where it needs replacing. 

I would in some cases offer our landlord to handle having things fixed, and then hand a receipt for the cost and have that deducted from the rent. E.g. if hte TV fell off the wall and broke in half (something not fixable that needs to be replaced) just go get another China brand TV at a agreed pricelevel. 

We are so fortunate to live in a new building where the construction company are actually fixing things as a warrenty kind of thing. But we do right now have water leaking in the kitchen and we'll just get that fixed ourselves. We do have a very flexible landlord, who also doesn't want to be bothered with having to do something every month, so we don't actually pay utilities every month, but only when it exceeds an amount the landlord thinks is worth dealing with. (every 3 months or so) 

I'd call the landlord and tell him: " the boiler is broken. Do you want to fix it or buy a new one? If you want to fix it, please let me know when the plumbers are coming, if you want to change it, please let me know when they're coming to change it or if you want me to go and buy a new one."

It's landlord responsibility to change or fix anything in the house. And is his responsibility to pay it.  

If you broke it on your own (which I doubt it) you should pay it... but in general, in China these things (boiler, ac, etc) get broken very often... so...

Once I got the fridge broken. It didn't freeze anymore. 

I called the landlady and she organized with the 'fixers'. Came home with them and fixed the whole thing. I didn't pay anything.

In the new apartment, the table was almost in pieces. I asked the landlord if we could have  a new one. He said ok, go to buy it and then I will deduct the cost of it from the next month rent. I went to Ikea, chose the table I wanted, before buying it I asked if the price was ok for him and also asked him if I could buy the chairs too. He agreed to everything. I bought the whole stuff, paid them and brought them at home. The month after I deducted the price of the table and chair from my rent.

They are not obligated to do it. In my experience it always worked meeting the landlord at least once before signing contract and see/feel how they behave, act and talk. To me that's enough to Itell if they are mfs just looking for someone to take the apt so they don't lose money or they are people using their brains to do fair biz and have acontent customer using their facilities.
Luckily I never had this trouble n landlord always have paid fixtures I need and changed broken electric or electronic devices for good ones, not only shitty ones from used devices store haha

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Unfortunately it's pot luck, usually if you're living in a complex the money you pay every month to pay for security and (communal) cleaning should cover minor repairs. Recently our boiler broke and after contacting a bunch of different people we found out need to pay 500 for spare parts, we spoke to our landlandy and she agreed to pay it. 

On the other hand she could have told us to shove it.

it really depends on who you rent from, are they decent and care about the tenants or do they just want to make some quick cash.

if you've just moved in recently I'd push to have them pay it all, if you've been there a while and they push you to pay then try and split it 50/50. If you're near the end of your contract you can tell them you'll just manage and move out later.

as a guide, a new boiler will cost around 1,000 plus installation. Depending where you buy they will probably send someone to install it.

according to the law,the landlord is responsible for repairing anything in the house,if he doesnt do anything after you tell him,you can have it fixed and he should pay,but you'd better let him know at first if you do so and give him a fapiao or receipt as a proof about how much you have paid for that so you could deduct the fee from your rent in the next month.when i have this problem,i usually ask the landlord to do the job.