Pumping over

plumber_UK · May 9, 2015

The issue I have is water pumping up the vent pipe into the f/e tank. For some reason the water level of the tank is not rising. The pumping over happens whether the system is hot or cold. Also the downstairs radiators are struggling to get warm.

I have checked the pump, I've cleaned and balanced the system but can't think of any other reason for this issue.

i can raise the vent pipe but not by much.

ive attached some pictures of the set up. The boiler is on the ground floor the hot water cylinder and pump on the 1st floor and the tanks in the loft space.
Ive attached a picture of the set up. Flow from boiler comes up the far right then runs horizontal, the first 22mm tee is the vent and the second tee is the feed. If you look closely you can see that someone
has put in a check valve on the feed. Would this have any affect?
any help would be appreciated

Ch4 plumbing · May 9, 2015

Cut the check valve out and replace with copper pipe, it shouldn't be there.

rocketmanbkk · May 9, 2015

Is the check valve above the pump please? Why isn't it supposed to be there?

Just learning, sorry!

Ch4 plumbing · May 9, 2015

The check valve shouldn't be there because it stops the water expanding back up into the F/E tank when it's heated, it's allowing cold water in but when heated the water expands and has nowhere to go other then over the vent.

Unregistered · May 9, 2015

I agree the check valve should not be there. But do you think that is the only problem ?

hammers4spanner · May 9, 2015

Unregistered said:
I agree the check valve should not be there. But do you think that is the only problem ?

remove it first

snowhead · May 9, 2015

I'd say it's previously be fitted in an uneducated attempt to try stop the pump over.

chris watkins · May 9, 2015

It certainly is why it is pumping over.

Water will be drawn in passed the check valve when the pump starts, then when full circulation is achieved & the water level (pressure) in system try's to stabilise back up the cold feed it can't get back past the check valve so has no option than come out of the open vent.

That is why it does it when cold as well as hot.

Simon F · May 9, 2015

problems also with downstairs rads, could be seriously blocked system.
are there cold spots in middle of rads?
blockage at neutral point as well as check valve issue.

are the downstairs valves fully open?
what height is the f+e above pump?
what size pump? how many rads? what size pipes?
what is pump speed set to?

has this always been a problem, or has it developed?

JCSPLUMBING · May 10, 2015

Open vent should be 450mm above the water level. No valves to be installed on the cold feed or vent. Check this first.

Elgordo · May 10, 2015

Definitely remove the check valve , it's a safety issue , it's the feed and expansion pipe and water when hot has to expand up through this . The vent pipe is the emergency vent in case of overheating or boiling . Pumping over can be a headache to rectify but this should fix it , best of luck !

Philip Lancaste · May 18, 2015

The NRV is acting like a blocked cold feed, even on a close coupled system this scenario happens.when the cold feed is blocked. System pump pressure is being diverted up open vent, removing NRV will stop pumping over and distribute system pump pressure around the system not up the open vent.