Difference between lifting system and pump station. Is this really necessary?

Hello everyone,

I am building a turnkey single-family house with a basement on a sloping plot. When I signed the offer, a lifting system for 2750€ was included in it, because the blackwater has to be pumped into the sewer, which is located above the basement.
The day before yesterday I received an email from the construction company, asking me to please confirm the additional price for sanitation. In the attached PDF, the lifting system was removed from the offer; instead, a pumping station is now necessary, which is considerably more expensive at 11,000€.

In response to my inquiry as to why this is suddenly required, I received the following answer:
Following feedback: Due to the building location and plot situation, it is not possible as usual and included in the contract to drain from the building using natural slope (sewer pipe slope to the inspection shaft).
Instead, a pressure system must be installed: all wastewater from the house is collected in the shaft and pumped into the sewer via a pressure pump and pressure pipe.
Reason: the channel of the existing plot inspection shaft is higher than the sewer pipes, which come out of the basement wall at frost-proof height.

So, a lifting system is not a pressure system, while a pumping station is one? The model proposed to me was advertised on the manufacturer's website as follows:
More performance is not possible. In the wet installation variant, the XYZ handles very large amounts of fecal-contaminated wastewater itself and is particularly suitable for commercial and industrial use.

That made me a bit suspicious. What I am building is a single-family house with a basement granny flat, so there are 2 kitchens and 2 bathrooms + 1 guest WC. Doesn’t the pumping station sound somewhat 'oversized' for that?

Now to the last point, where I am not sure: The originally planned lifting system was to be installed in the basement slab. The new pumping station will now be installed instead in an external shaft. Does the installation in the shaft offer me any advantages? On the one hand, I then have the shaft cover in the garden, directly(!) next to the terrace; on the other hand, the shaft probably needs to be vented from time to time. If I had the whole installation in the slab, nothing would protrude from the ground and the ventilation would then be done via the roof. Would an installation in the slab not be more reasonable for me?
If it is important: it is being built with a white tank.

Thanks for your help!
Stefan

In the lifting station, the pump basically pushes the water upwards and then it drains normally. In a pumping station, you have a pressure pipe that is connected directly to the sewer or inspection chamber. From the pumping station onwards, no gradient is necessary. To determine what you need or to check if someone is fooling you, a drainage plan and an elevation profile are necessary. The reason sounds plausible at first. Additional costs also fit according to my experience. What do you do with the rainwater?

Hello teh_M,

thank you very much for your reply. I just took a look at the plans, attached is a section of the basement:


If I’m not completely mistaken, the differences in height relate to the floor of the ground floor, as the basement is at -2.6m. This would mean that the existing shaft in the top left ends just under 2m above the basement floor slab, so significantly higher.

In this respect, the pump station would probably be correct here. I was not informed about stormwater, but according to the plan there is a soakaway shaft to the east, the rain gutters are connected to this.

Is there a specific reason why underground pump stations are used instead of installing them into the floor slab? Somehow I can get used to the additional shaft next to the terrace if everything could also be placed under the basement.

Regards Stefan

That sounds plausible to me. However, it could have been clear from the beginning; the situation is not unexpected…

We have the same situation and also an external shaft with 2 pumps that switch on alternately at a certain level. It has been working without any problems except for a small defect for 20 years. In our case, however, that thing is called a lift station…

Hello k-man,

thank you for your response. I also find it somewhat unfortunate that the significantly higher costs for the pumping station have come to light just before construction begins. However, I am not sure whether one can expect the construction company to have considered everything during the bidding phase, such as the canal depth. It is what it is now, I guess I will have to bear the costs.

I am still torn between installation in the ground or in the base slab, since it seems that every source on the internet says something different about this :)

Is the ventilation done via the roof in your case?

We are glad that the installation is NOT in the floor slab... you don't want to have the smell in the house when the thing needs to be opened! Besides, the pumps have real power, and you also don't want to hear them running throughout the whole house. There is no ventilation with us, and it doesn't smell either.

I would make sure that 2 pumps are installed for the price... otherwise, you have a problem if something goes wrong with one, or you pay for emergency service. Our system is ABS Synconta, which I can recommend. The control unit should be frost-free, for example in the basement. The distance between the control unit and the shaft should be as short as possible due to the type of level measurement.