Any issues with oversized (blue) domestic pressure vessel

Calahonda52

existing is a 12litre
bladder is gone
only one I get get quickly is an 18 Litre one
just wonder are there any issues re fitting the 18 instead of the 12, i.e. oversizing it.
Setup is 3 bar pump on cold water and pressurised Hot water cylinder and well as the cold
thanks

Calahonda52

The above, 18 L vessel has just failed.
Wont take any air and there is some seepage through the 3 bar PRV
No sign of leakage from the PV, is the bladder replaceable?
Thanks

Wearb

Calahonda52 wrote: »

The above, 18 L vessel has just failed.
Wont take any air and there is some seepage through the 3 bar PRV
No sign of leakage from the PV, is the bladder replaceable?
Thanks

Is there water coming through the Schrader valve when depressed?
The replaceable bladders have a ring of bolts on them. Rarely worth the bother.

fully floating

If there is a flange bolted to the end you can change the bladder, but it's usually not cost effective, if you are badly stuck you could try putting a patch on it like a bike tube patch but they are usually to far gone for that and won't last very long.

Dtp1979

Calahonda52 wrote: »

The above, 18 L vessel has just failed.
Wont take any air and there is some seepage through the 3 bar PRV
No sign of leakage from the PV, is the bladder replaceable?
Thanks

Pretty sure it should be a 6/7 bar valve. Plus are you pressurising it when the pump off and taps open?
What size cylinder do u have?

Calahonda52

Thanks guys, can't multi quote so
Wearb: no leak at valve, yes bolted
Dtp1979: setting pressure to 1,5 bar with system fully depressurised as you suggest
cylinder is 125L
the last PRV lasted 20 years, this is 8 months
the Pressure reducing valve is preset at 3.5 bar
the pressure relief valve is 6 bar, so my apologies for the earlier guess

Dtp1979

Calahonda52 wrote: »

Thanks guys, can't multi quote so
Wearb: no leak at valve, yes bolted
Dtp1979: setting pressure to 1,5 bar with system fully depressurised as you suggest
cylinder is 125L
the last PRV lasted 20 years, this is 8 months
the Pressure reducing valve is preset at 3.5 bar
the pressure relief valve is 6 bar, so my apologies for the earlier guess

The vessel pressure should be set around the max incoming pressure. 18l is perfect. No harm even going bigger
Assuming this vessel is for hot water expansion?

Calahonda52

Wearb wrote: »

Is there water coming through the Schrader valve when depressed?
The replaceable bladders have a ring of bolts on them. Rarely worth the bother.

fully floating wrote: »

If there is a flange bolted to the end you can change the bladder, but it's usually not cost effective, if you are badly stuck you could try putting a patch on it like a bike tube patch but they are usually to far gone for that and won't last very long.

Dtp1979 wrote: »

Pretty sure it should be a 6/7 bar valve. Plus are you pressurising it when the pump off and taps open?
What size cylinder do u have?

Dtp1979 wrote: »

The vessel pressure should be set around the max incoming pressure. 18l is perfect. No harm even going bigger
Assuming this vessel is for hot water expansion?

Thanks, the cold water pump maxes out about 3.5 so should I pressurise the vessel to that , with system depressurised?

Calahonda52

Calahonda52 wrote: »

Thanks, the cold water pump maxes out about 3.5 so should I pressurise the vessel to that , with system depressurised?

Correct.

Calahonda52

Okay, thanks for all the responses:
The OH has observed that now with no vessel, the pump clicks in v quickly which means hot and cold get delivered simultaneously.
When the 18LPV, which replaced a 12L, was working, the hot could run for a while before the pump clicked in, this meant the shower mixer tap needed to start on cold, never popular with the OH
What is happening now is that the Pressure relief valve is leaking a bit when the hot water is being heated, I have it down low but not ideal i know.
The question is: should I got back to 12 or even smaller
Its a 125L HW cylinder

Calahonda52

Calahonda52 wrote: »

Okay, thanks for all the responses:
The OH has observed that now with no vessel, the pump clicks in v quickly which means hot and cold get delivered simultaneously.
When the 18LPV, which replaced a 12L, was working, the hot could run for a while before the pump clicked in, this meant the shower mixer tap needed to start on cold, never popular with the OH
What is happening now is that the Pressure relief valve is leaking a bit when the hot water is being heated, I have it down low but not ideal i know.
The question is: should I got back to 12 or even smaller
Its a 125L HW cylinder

Is there a expansion vessel fitted to absorb the expansion of the heated water in the cylinder?

A dripping safety valve is a indicator that there is a problem with a invented cylinder installation and would be linked to a lack of expansion vessel (if that's the case)



With a expansion vessel they can store pressure (much larger ones called accumulators are used instead of pumps) so that when you open a hot tap there can be a slight delay between the hot tap opening and the pump kicking in due to the stored pressure in the expansion vessel, the larger the expansion vessel the longer the potential delay.

Calahonda52

Thanks, yes, this blue one is on the hot side and is "flat" hence the seep for the reason you said.
I think I will go back to the 12l, it lasted 15 years or so, the 18L 8 months...

Wearb

Calahonda52 wrote: »

Thanks, yes, this blue one is on the hot side and is "flat" hence the seep for the reason you said.
I think I will go back to the 12l, it lasted 15 years or so, the 18L 8 months...

The size of the EV doesn't matter as long as it isn't too small to take the expansion. Going from 18 to 12 or visa versa isn't going to make any difference at all, assuming that 12 was correctly sized in the first place.
The bigger EV will mean less cycling for the pump and may even prolong it's life.

Wearb

Calahonda52 wrote: »

Thanks, yes, this blue one is on the hot side and is "flat" hence the seep for the reason you said.
I think I will go back to the 12l, it lasted 15 years or so, the 18L 8 months...

If the EV is flat, I am surprised that you are not getting a lot more than a seep. Perhaps there is still some air between the metal of the EV and the water that is acting as a buffer.
I wouldn't leave it too long without fixing. The EV also acts a a safety for the expansion. Think of what might happen is safety valve stuck closed and EV was flat.

hatchman

Calahonda52 wrote:

Thanks, yes, this blue one is on the hot side and is "flat" hence the seep for the reason you said. I think I will go back to the 12l, it lasted 15 years or so, the 18L 8 months...

There are two different uses for these vessels. Depending on it location and the pressure it is set at, it can be set up as either a pressure vessel or an expansion vessel. If the pressure is set too low and it is located on the cold feed to your pressurised hot water cylinder it will act as a pressure vessel for the hot water only and I think this maybe is what you are experiencing. Have a look at the website pumpanswers.com and look for the explanations on vessels.