heatrae sadia, water stop flowing

[josh patterson]

I have an heatrae sadia FBM water heater. recently, when the water is heating up, after its been on for 15-20 mins the water stop flowing. its starts to slow up and then stops completely.

any ideas on how to fix it?
any help would be greatly appreciated.

thanks.

 

[josh patterson]

i forgot to mention that after any where between 4 to 24 hours later the water starts to flow again. then once turned back on i get the same problem all over again

 

[EFLImpudence]

Plumbing forum ?

I'll ask for it to be moved.

 

[josh patterson]

Thank you

 

[Nige F]

Have a look in the top - there is apparently a ballvalve there it's probably stuck.

 

[josh patterson]

hi Nige F, the ballvalve is ok, thats what i thought it was. do you know if there's something inside that would swell from heat? because thats what it seems like. The water heats up and the flow slows down and eventually stops. Then when i turn it off and it has had time to cool down the water starts to flow again.

 

[simond]

Does it have a blending valve on the outlet, many have this option fitted?

If this goes wrong it can reduce the supply of hot water when the temperature rises.....also, if the supply of cold water to the blending valve is interrupted a similar problem will result when the stored water heats up.

 

[josh patterson]

Hi simond, there's no blender valve. just mains cold to the top, an over flow and the hot water outlet is at the bottom.

 

[josh patterson]

ok, so i think i might have found the problem. the hot outflow pipe has 2 bends in it before it goes straight down and disapears into the wall. i can hear the water just trickling through as it fall down to the bottom of the pipe. would that be a limescale build up? i still dont know how that relates to the water getting hot and no water coming out? can i put descaler straight into a boiler?

many thanks

 

[Nige F]

Before using a chemical descaler I would take out the wiring from the heater @ the bottom and the thermostats out their pockets- open that drain cock and after draining back flush through the cock- that should loosen scale. I'm thinking if you try and dissolve it you might end up with a mess that you can't clear out of the tank.

 

[josh patterson]

Nice one Nige F!! i have tuesday off so will be giving that a go. really appreciate the replies, thanks

 

[Nige F]

Keep us posted

 

[josh patterson]

ive been at the water heater all day to no avail. i drained it, took the element out, cleaned out the very little limescale that was inside (had the element replaced about 6 months ago). flushed the pipe from the ballvalve through to the water heater. i did it back up, filled it and the water was coming through great. about 30 -45 mins after i turned it on to heat, the water stopped coming through again. its like something is expanding with the heat of the water and constricting the pipe. when the water in the heater cools down the water starts flowing again. im pretty much ready to take the element out and throw that in the bath instead,lol

 

[josh patterson]

ok, so ive narrowed the problem down, its not the boiler it the hot water outlet pipe. i took it off but there was nothing in the first length, im guessing its just after the first bend. does anyone no what it could be? its fine when the water is cold but stops when its hot. does limescale expand with heat?

 

[josh patterson]

lol, it wasnt the pipes . i put a small tap directly on the hot water outlet where the pipe used to be. when its heats up the water stops but if i open up the tap, pressurized air comes out followed by the hot water!!! any ideas?