Pipe size problems

[Plamber]

Evening all,

I'm working in a block where all the flats have constant hot water and central heating(they pay a set amount each month set by landlord).

The 2 top flats baths hot water taps are spluttering water when turned on, i looked back to the main supply pipe(22mm) and noticed that the pipe going to the bathroom is 15mm, then about a meter before the bath it ups to 22mm, would this cause the hot taps to splutter??

 

[justlead1]

Hi. No it would not. Probably the demand of flats at lower level.

 

[Plamber]

it happens when tennants in the lower floors are out, there is only 4 flats in the block, 1 per floor and its happening to the top 2 floors. its puzzled me. any ideas?

 

[moony]

what sort of system is it ?

 

[Plamber]

not sure what its called, its a massive boiler and hot water cylender in the basement and it pumps around both blocks so they have instant hot water and heating all day everyday. it going up to the roofspace and back down, its pumped on a loop. but two of the flats have splutering hot water in the bath. sorry but thats all i can tell you now.

hopefully im going to have a look at the plans tomorrow and i should learn more then.

 

[moony]

and you've checked the pumps i take it ? probably know more when you look at the plans but sounds like a problem with the pumps.

 

[Renewable M]

if they are old pumps they could be lazy and n.o.t q..u..i..t..e m...a...k...i...n...g i....t, hence the sputtering.

I will admit, this is a shot in the dark... but could be the one.

If there is a lot of positive pressure though when it sputters, i have my doubts. Then I would check whatever NRV is letting the water into the DHW circuit.

Be interested to know how this one progresses.

 

[justlead1]

Hi. Sounds like an open vented hot water system. The pump/circulater on the secondary return may be pulling air via vent pipe. I would check this by streching a kid balloon over the vent pipe end. Then drawing water for a bit and monitor results. Good Luck

 

[Plamber]

hi all, no justlead1 its an unvented system, it is pumping hot water up to the roofspace then dropping down at 2 different points to feed each block, then the water i assume just keeps moving around the system when not used. its so the tennants can have instant hot water. it used to the a YMCA builiding and the old system was kept, just upgraded.

the point it splutters is the furthest away block and the 2 top floors, its strange because the 2 flats at the bottom aren't having any problems. the only thing i noticed is that from the main pipe to these flats its a 15mm pipe going to the bath and whb, but just before the bath it ups to 22mm for the bath then goes back down to 15mm for the whb. but that wouldnt cause it to splutter would it? the pressure is also fine.

 

[Blackcatgas]

How many floors high are the flats? if the incoming mains pressure is 2 bar thats the eq of 20meters head, if you were to attach 20m of hose pipe off a 2 bar supply and run it verticly upwards it wouldnt have the pressure to come out of the end of the pipe, big blocks of flats etc have big booster packs the size of wardrobes and break tanks every few floors up. to get the supply to the top of the building.

 

[justlead1]

Hi. Thanks for reply, apologise for error. It still sounds like it pulling air somewhere. It is possiable that when demand is at its greatest the upper floors get starved (negative pressure) air could be drawn via an open tap. Have any of the tenants experienced poor supply at times? Good Luck

 

[Plamber]

No everyones pressure is more than enough, even when running lots of hot taps at the same time! the 2 flats that are having the spluttering problems have really good pressure which i'm finding strange. it sounds exactly like its pulling in air from somewhere. was there today with 2 other (quite experienced) plumbers and were quite confused.

I even replaced the tap cylenders (desperate attempt) incase it was them.

 

[justlead1]

i. Good Luck with it. When you crack it let me know how?

 

[Blackcatgas]

Hi. Thanks for reply, apologise for error. It still sounds like it pulling air somewhere. It is possiable that when demand is at its greatest the upper floors get starved (negative pressure) air could be drawn via an open tap. Have any of the tenants experienced poor supply at times? Good Luck

Or an AAV? but I dont know why theyd have used one on a presurised system.

 

[justlead1]

Hi. Check out tread "air locks" today. Its all new to me but might be the answer to your problem? Good Luck

 

[Plamber]

yeah thanks, i posted that on "air locks".

i've changed the cylenders just incase too see whats what. ive been away from the job for a fews days now and i think im going back either tomorrow or wed so we'll just have to see what i can do.

the plumbing plan shows nothing so im going back to the roofspace to see if i missed aything. maybe even install an AAV cos it really sounds like air. what you rekon?

 

[Plamber]

Evening all, Today i finaly got back to this job after a few very busy days (phew) and i think i've cracked it. this morning i discovered that the system DOES have a vent pipe from the very big and very complicated boiler/cylender contraption.

in a 3rd and almost unaccessable hidden loft. i also found a gate valve on the HW return pipe that was nearly shut, so i opened it fully and the spluttering seems to have stopped. would the half closed valve have caused the spluttering? anyway im very relieved for now.

 

[justlead1]

Hi. It could well be the problem, by restricting the circulation and causing a negative head at a point where the vent joins the system. Lets hope its cured long term. Good Luck

 

[Plamber]

just heard this morning that its still spluttering at late evenings and in mornings in 4 flats that have baths, seems to me like its a pump problem. pumps struggling at bed times and mornings due to more demand.

 

[justlead1]

Hi. Try the french letter/ kids ballon over the vent you found, see what happens. You could do with a historiographer of the daily/weekly pressure, to see if it coincides with the problem. Good Luck